perlapi

PERLAPI(1)             Perl Programmers Reference Guide             PERLAPI(1)

NAME
       perlapi - autogenerated documentation for the perl public API

DESCRIPTION
       This file contains the documentation of the perl public API generated
       by embed.pl, specifically a listing of functions, macros, flags, and
       variables that may be used by extension writers.  At the end is a list
       of functions which have yet to be documented.  The interfaces of those
       are subject to change without notice.  Anything not listed here is not
       part of the public API, and should not be used by extension writers at
       all.  For these reasons, blindly using functions listed in proto.h is
       to be avoided when writing extensions.

       In Perl, unlike C, a string of characters may generally contain
       embedded "NUL" characters.  Sometimes in the documentation a Perl
       string is referred to as a "buffer" to distinguish it from a C string,
       but sometimes they are both just referred to as strings.

       Note that all Perl API global variables must be referenced with the
       "PL_" prefix.  Again, those not listed here are not to be used by
       extension writers, and can be changed or removed without notice; same
       with macros.  Some macros are provided for compatibility with the
       older, unadorned names, but this support may be disabled in a future
       release.

       Perl was originally written to handle US-ASCII only (that is characters
       whose ordinal numbers are in the range 0 - 127).  And documentation and
       comments may still use the term ASCII, when sometimes in fact the
       entire range from 0 - 255 is meant.

       The non-ASCII characters below 256 can have various meanings, depending
       on various things.  (See, most notably, perllocale.)  But usually the
       whole range can be referred to as ISO-8859-1.  Often, the term
       "Latin-1" (or "Latin1") is used as an equivalent for ISO-8859-1.  But
       some people treat "Latin1" as referring just to the characters in the
       range 128 through 255, or somethimes from 160 through 255.  This
       documentation uses "Latin1" and "Latin-1" to refer to all 256
       characters.

       Note that Perl can be compiled and run under either ASCII or EBCDIC
       (See perlebcdic).  Most of the documentation (and even comments in the
       code) ignore the EBCDIC possibility.  For almost all purposes the
       differences are transparent.  As an example, under EBCDIC, instead of
       UTF-8, UTF-EBCDIC is used to encode Unicode strings, and so whenever
       this documentation refers to "utf8" (and variants of that name,
       including in function names), it also (essentially transparently) means
       "UTF-EBCDIC".  But the ordinals of characters differ between ASCII,
       EBCDIC, and the UTF- encodings, and a string encoded in UTF-EBCDIC may
       occupy a different number of bytes than in UTF-8.

       The listing below is alphabetical, case insensitive.

Array Manipulation Functions
       av_clear
               Frees the all the elements of an array, leaving it empty.  The
               XS equivalent of "@array = ()".  See also "av_undef".

               Note that it is possible that the actions of a destructor
               called directly or indirectly by freeing an element of the
               array could cause the reference count of the array itself to be
               reduced (e.g. by deleting an entry in the symbol table). So it
               is a possibility that the AV could have been freed (or even
               reallocated) on return from the call unless you hold a
               reference to it.

                       void    av_clear(AV *av)

       av_create_and_push
               NOTE: this function is experimental and may change or be
               removed without notice.

               Push an SV onto the end of the array, creating the array if
               necessary.  A small internal helper function to remove a
               commonly duplicated idiom.

                       void    av_create_and_push(AV **const avp,
                                                  SV *const val)

       av_create_and_unshift_one
               NOTE: this function is experimental and may change or be
               removed without notice.

               Unshifts an SV onto the beginning of the array, creating the
               array if necessary.  A small internal helper function to remove
               a commonly duplicated idiom.

                       SV**    av_create_and_unshift_one(AV **const avp,
                                                         SV *const val)

       av_delete
               Deletes the element indexed by "key" from the array, makes the
               element mortal, and returns it.  If "flags" equals "G_DISCARD",
               the element is freed and NULL is returned. NULL is also
               returned if "key" is out of range.

               Perl equivalent: "splice(@myarray,$key,1,undef)" (with the
               "splice" in void context if "G_DISCARD" is present).

                       SV*     av_delete(AV *av, SSize_t key, I32 flags)

       av_exists
               Returns true if the element indexed by "key" has been
               initialized.

               This relies on the fact that uninitialized array elements are
               set to "NULL".

               Perl equivalent: "exists($myarray[$key])".

                       bool    av_exists(AV *av, SSize_t key)

       av_extend
               Pre-extend an array.  The "key" is the index to which the array
               should be extended.

                       void    av_extend(AV *av, SSize_t key)

       av_fetch
               Returns the SV at the specified index in the array.  The "key"
               is the index.  If lval is true, you are guaranteed to get a
               real SV back (in case it wasn't real before), which you can
               then modify.  Check that the return value is non-null before
               dereferencing it to a "SV*".

               See "Understanding the Magic of Tied Hashes and Arrays" in
               perlguts for more information on how to use this function on
               tied arrays.

               The rough perl equivalent is $myarray[$key].

                       SV**    av_fetch(AV *av, SSize_t key, I32 lval)

       AvFILL  Same as "av_top_index()" or "av_tindex()".

                       int     AvFILL(AV* av)

       av_fill Set the highest index in the array to the given number,
               equivalent to Perl's "$#array=$fill;".

               The number of elements in the array will be "fill+1" after
               "av_fill()" returns.  If the array was previously shorter, then
               the additional elements appended are set to NULL.  If the array
               was longer, then the excess elements are freed.
               "av_fill(av,-1)" is the same as "av_clear(av)".

                       void    av_fill(AV *av, SSize_t fill)

       av_len  Same as "av_top_index".  Note that, unlike what the name
               implies, it returns the highest index in the array, so to get
               the size of the array you need to use "av_len(av)+1".  This is
               unlike "sv_len", which returns what you would expect.

                       SSize_t av_len(AV *av)

       av_make Creates a new AV and populates it with a list of SVs.  The SVs
               are copied into the array, so they may be freed after the call
               to "av_make".  The new AV will have a reference count of 1.

               Perl equivalent: "my @new_array = ($scalar1, $scalar2,
               $scalar3...);"

                       AV*     av_make(SSize_t size, SV **strp)

       av_pop  Removes one SV from the end of the array, reducing its size by
               one and returning the SV (transferring control of one reference
               count) to the caller.  Returns &PL_sv_undef if the array is
               empty.

               Perl equivalent: "pop(@myarray);"

                       SV*     av_pop(AV *av)

       av_push Pushes an SV (transferring control of one reference count) onto
               the end of the array.  The array will grow automatically to
               accommodate the addition.

               Perl equivalent: "push @myarray, $val;".

                       void    av_push(AV *av, SV *val)

       av_shift
               Removes one SV from the start of the array, reducing its size
               by one and returning the SV (transferring control of one
               reference count) to the caller.  Returns &PL_sv_undef if the
               array is empty.

               Perl equivalent: "shift(@myarray);"

                       SV*     av_shift(AV *av)

       av_store
               Stores an SV in an array.  The array index is specified as
               "key".  The return value will be "NULL" if the operation failed
               or if the value did not need to be actually stored within the
               array (as in the case of tied arrays).  Otherwise, it can be
               dereferenced to get the "SV*" that was stored there (= "val")).

               Note that the caller is responsible for suitably incrementing
               the reference count of "val" before the call, and decrementing
               it if the function returned "NULL".

               Approximate Perl equivalent: "splice(@myarray, $key, 1, $val)".

               See "Understanding the Magic of Tied Hashes and Arrays" in
               perlguts for more information on how to use this function on
               tied arrays.

                       SV**    av_store(AV *av, SSize_t key, SV *val)

       av_tindex
               Same as "av_top_index()".

                       int     av_tindex(AV* av)

       av_top_index
               Returns the highest index in the array.  The number of elements
               in the array is "av_top_index(av)+1".  Returns -1 if the array
               is empty.

               The Perl equivalent for this is $#myarray.

               (A slightly shorter form is "av_tindex".)

                       SSize_t av_top_index(AV *av)

       av_undef
               Undefines the array. The XS equivalent of "undef(@array)".

               As well as freeing all the elements of the array (like
               "av_clear()"), this also frees the memory used by the av to
               store its list of scalars.

               See "av_clear" for a note about the array possibly being
               invalid on return.

                       void    av_undef(AV *av)

       av_unshift
               Unshift the given number of "undef" values onto the beginning
               of the array.  The array will grow automatically to accommodate
               the addition.

               Perl equivalent: "unshift@myarray,((undef)x$num);"

                       void    av_unshift(AV *av, SSize_t num)

       get_av  Returns the AV of the specified Perl global or package array
               with the given name (so it won't work on lexical variables).
               "flags" are passed to "gv_fetchpv".  If "GV_ADD" is set and the
               Perl variable does not exist then it will be created.  If
               "flags" is zero and the variable does not exist then NULL is
               returned.

               Perl equivalent: "@{"$name"}".

               NOTE: the perl_ form of this function is deprecated.

                       AV*     get_av(const char *name, I32 flags)

       newAV   Creates a new AV.  The reference count is set to 1.

               Perl equivalent: "my @array;".

                       AV*     newAV()

       sortsv  In-place sort an array of SV pointers with the given comparison
               routine.

               Currently this always uses mergesort.  See "sortsv_flags" for a
               more flexible routine.

                       void    sortsv(SV** array, size_t num_elts,
                                      SVCOMPARE_t cmp)

Callback Functions
       call_argv
               Performs a callback to the specified named and package-scoped
               Perl subroutine with "argv" (a "NULL"-terminated array of
               strings) as arguments.  See perlcall.

               Approximate Perl equivalent: "&{"$sub_name"}(@$argv)".

               NOTE: the perl_ form of this function is deprecated.

                       I32     call_argv(const char* sub_name, I32 flags,
                                         char** argv)

       call_method
               Performs a callback to the specified Perl method.  The blessed
               object must be on the stack.  See perlcall.

               NOTE: the perl_ form of this function is deprecated.

                       I32     call_method(const char* methname, I32 flags)

       call_pv Performs a callback to the specified Perl sub.  See perlcall.

               NOTE: the perl_ form of this function is deprecated.

                       I32     call_pv(const char* sub_name, I32 flags)

       call_sv Performs a callback to the Perl sub specified by the SV.

               If neither the "G_METHOD" nor "G_METHOD_NAMED" flag is
               supplied, the SV may be any of a CV, a GV, a reference to a CV,
               a reference to a GV or "SvPV(sv)" will be used as the name of
               the sub to call.

               If the "G_METHOD" flag is supplied, the SV may be a reference
               to a CV or "SvPV(sv)" will be used as the name of the method to
               call.

               If the "G_METHOD_NAMED" flag is supplied, "SvPV(sv)" will be
               used as the name of the method to call.

               Some other values are treated specially for internal use and
               should not be depended on.

               See perlcall.

               NOTE: the perl_ form of this function is deprecated.

                       I32     call_sv(SV* sv, volatile I32 flags)

       ENTER   Opening bracket on a callback.  See "LEAVE" and perlcall.

                               ENTER;

       ENTER_with_name(name)
               Same as "ENTER", but when debugging is enabled it also
               associates the given literal string with the new scope.

                               ENTER_with_name(name);

       eval_pv Tells Perl to "eval" the given string in scalar context and
               return an SV* result.

               NOTE: the perl_ form of this function is deprecated.

                       SV*     eval_pv(const char* p, I32 croak_on_error)

       eval_sv Tells Perl to "eval" the string in the SV.  It supports the
               same flags as "call_sv", with the obvious exception of
               "G_EVAL".  See perlcall.

               NOTE: the perl_ form of this function is deprecated.

                       I32     eval_sv(SV* sv, I32 flags)

       FREETMPS
               Closing bracket for temporaries on a callback.  See "SAVETMPS"
               and perlcall.

                               FREETMPS;

       LEAVE   Closing bracket on a callback.  See "ENTER" and perlcall.

                               LEAVE;

       LEAVE_with_name(name)
               Same as "LEAVE", but when debugging is enabled it first checks
               that the scope has the given name. "name" must be a literal
               string.

                               LEAVE_with_name(name);

       SAVETMPS
               Opening bracket for temporaries on a callback.  See "FREETMPS"
               and perlcall.

                               SAVETMPS;

Character case changing
       Perl uses "full" Unicode case mappings.  This means that converting a
       single character to another case may result in a sequence of more than
       one character.  For example, the uppercase of "ss" (LATIN SMALL LETTER
       SHARP S) is the two character sequence "SS".  This presents some
       complications   The lowercase of all characters in the range 0..255 is
       a single character, and thus "toLOWER_L1" is furnished.  But,
       "toUPPER_L1" can't exist, as it couldn't return a valid result for all
       legal inputs.  Instead "toUPPER_uvchr" has an API that does allow every
       possible legal result to be returned.)  Likewise no other function that
       is crippled by not being able to give the correct results for the full
       range of possible inputs has been implemented here.

       toFOLD  Converts the specified character to foldcase.  If the input is
               anything but an ASCII uppercase character, that input character
               itself is returned.  Variant "toFOLD_A" is equivalent.  (There
               is no equivalent "to_FOLD_L1" for the full Latin1 range, as the
               full generality of "toFOLD_uvchr" is needed there.)

                       U8      toFOLD(U8 ch)

       toFOLD_utf8
               This is like "toFOLD_utf8_safe", but doesn't have the "e"
               parameter  The function therefore can't check if it is reading
               beyond the end of the string.  Starting in Perl v5.30, it will
               take the "e" parameter, becoming a synonym for
               "toFOLD_utf8_safe".  At that time every program that uses it
               will have to be changed to successfully compile.  In the
               meantime, the first runtime call to "toFOLD_utf8" from each
               call point in the program will raise a deprecation warning,
               enabled by default.  You can convert your program now to use
               "toFOLD_utf8_safe", and avoid the warnings, and get an extra
               measure of protection, or you can wait until v5.30, when you'll
               be forced to add the "e" parameter.

                       UV      toFOLD_utf8(U8* p, U8* s, STRLEN* lenp)

       toFOLD_utf8_safe
               Converts the first UTF-8 encoded character in the sequence
               starting at "p" and extending no further than "e-1" to its
               foldcase version, and stores that in UTF-8 in "s", and its
               length in bytes in "lenp".  Note that the buffer pointed to by
               "s" needs to be at least "UTF8_MAXBYTES_CASE+1" bytes since the
               foldcase version may be longer than the original character.

               The first code point of the foldcased version is returned (but
               note, as explained at the top of this section, that there may
               be more).

               The suffix "_safe" in the function's name indicates that it
               will not attempt to read beyond "e-1", provided that the
               constraint "s<e" is true (this is asserted for in "-DDEBUGGING"
               builds).  If the UTF-8 for the input character is malformed in
               some way, the program may croak, or the function may return the
               REPLACEMENT CHARACTER, at the discretion of the implementation,
               and subject to change in future releases.

                       UV      toFOLD_utf8_safe(U8* p, U8* e, U8* s,
                                                STRLEN* lenp)

       toFOLD_uvchr
               Converts the code point "cp" to its foldcase version, and
               stores that in UTF-8 in "s", and its length in bytes in "lenp".
               The code point is interpreted as native if less than 256;
               otherwise as Unicode.  Note that the buffer pointed to by "s"
               needs to be at least "UTF8_MAXBYTES_CASE+1" bytes since the
               foldcase version may be longer than the original character.

               The first code point of the foldcased version is returned (but
               note, as explained at the top of this section, that there may
               be more).

                       UV      toFOLD_uvchr(UV cp, U8* s, STRLEN* lenp)

       toLOWER Converts the specified character to lowercase.  If the input is
               anything but an ASCII uppercase character, that input character
               itself is returned.  Variant "toLOWER_A" is equivalent.

                       U8      toLOWER(U8 ch)

       toLOWER_L1
               Converts the specified Latin1 character to lowercase.  The
               results are undefined if the input doesn't fit in a byte.

                       U8      toLOWER_L1(U8 ch)

       toLOWER_LC
               Converts the specified character to lowercase using the current
               locale's rules, if possible; otherwise returns the input
               character itself.

                       U8      toLOWER_LC(U8 ch)

       toLOWER_utf8
               This is like "toLOWER_utf8_safe", but doesn't have the "e"
               parameter  The function therefore can't check if it is reading
               beyond the end of the string.  Starting in Perl v5.30, it will
               take the "e" parameter, becoming a synonym for
               "toLOWER_utf8_safe".  At that time every program that uses it
               will have to be changed to successfully compile.  In the
               meantime, the first runtime call to "toLOWER_utf8" from each
               call point in the program will raise a deprecation warning,
               enabled by default.  You can convert your program now to use
               "toLOWER_utf8_safe", and avoid the warnings, and get an extra
               measure of protection, or you can wait until v5.30, when you'll
               be forced to add the "e" parameter.

                       UV      toLOWER_utf8(U8* p, U8* s, STRLEN* lenp)

       toLOWER_utf8_safe
               Converts the first UTF-8 encoded character in the sequence
               starting at "p" and extending no further than "e-1" to its
               lowercase version, and stores that in UTF-8 in "s", and its
               length in bytes in "lenp".  Note that the buffer pointed to by
               "s" needs to be at least "UTF8_MAXBYTES_CASE+1" bytes since the
               lowercase version may be longer than the original character.

               The first code point of the lowercased version is returned (but
               note, as explained at the top of this section, that there may
               be more).

               The suffix "_safe" in the function's name indicates that it
               will not attempt to read beyond "e-1", provided that the
               constraint "s<e" is true (this is asserted for in "-DDEBUGGING"
               builds).  If the UTF-8 for the input character is malformed in
               some way, the program may croak, or the function may return the
               REPLACEMENT CHARACTER, at the discretion of the implementation,
               and subject to change in future releases.

                       UV      toLOWER_utf8_safe(U8* p, U8* e, U8* s,
                                                 STRLEN* lenp)

       toLOWER_uvchr
               Converts the code point "cp" to its lowercase version, and
               stores that in UTF-8 in "s", and its length in bytes in "lenp".
               The code point is interpreted as native if less than 256;
               otherwise as Unicode.  Note that the buffer pointed to by "s"
               needs to be at least "UTF8_MAXBYTES_CASE+1" bytes since the
               lowercase version may be longer than the original character.

               The first code point of the lowercased version is returned (but
               note, as explained at the top of this section, that there may
               be more).

                       UV      toLOWER_uvchr(UV cp, U8* s, STRLEN* lenp)

       toTITLE Converts the specified character to titlecase.  If the input is
               anything but an ASCII lowercase character, that input character
               itself is returned.  Variant "toTITLE_A" is equivalent.  (There
               is no "toTITLE_L1" for the full Latin1 range, as the full
               generality of "toTITLE_uvchr" is needed there.  Titlecase is
               not a concept used in locale handling, so there is no
               functionality for that.)

                       U8      toTITLE(U8 ch)

       toTITLE_utf8
               This is like "toLOWER_utf8_safe", but doesn't have the "e"
               parameter  The function therefore can't check if it is reading
               beyond the end of the string.  Starting in Perl v5.30, it will
               take the "e" parameter, becoming a synonym for
               "toTITLE_utf8_safe".  At that time every program that uses it
               will have to be changed to successfully compile.  In the
               meantime, the first runtime call to "toTITLE_utf8" from each
               call point in the program will raise a deprecation warning,
               enabled by default.  You can convert your program now to use
               "toTITLE_utf8_safe", and avoid the warnings, and get an extra
               measure of protection, or you can wait until v5.30, when you'll
               be forced to add the "e" parameter.

                       UV      toTITLE_utf8(U8* p, U8* s, STRLEN* lenp)

       toTITLE_utf8_safe
               Converts the first UTF-8 encoded character in the sequence
               starting at "p" and extending no further than "e-1" to its
               titlecase version, and stores that in UTF-8 in "s", and its
               length in bytes in "lenp".  Note that the buffer pointed to by
               "s" needs to be at least "UTF8_MAXBYTES_CASE+1" bytes since the
               titlecase version may be longer than the original character.

               The first code point of the titlecased version is returned (but
               note, as explained at the top of this section, that there may
               be more).

               The suffix "_safe" in the function's name indicates that it
               will not attempt to read beyond "e-1", provided that the
               constraint "s<e" is true (this is asserted for in "-DDEBUGGING"
               builds).  If the UTF-8 for the input character is malformed in
               some way, the program may croak, or the function may return the
               REPLACEMENT CHARACTER, at the discretion of the implementation,
               and subject to change in future releases.

                       UV      toTITLE_utf8_safe(U8* p, U8* e, U8* s,
                                                 STRLEN* lenp)

       toTITLE_uvchr
               Converts the code point "cp" to its titlecase version, and
               stores that in UTF-8 in "s", and its length in bytes in "lenp".
               The code point is interpreted as native if less than 256;
               otherwise as Unicode.  Note that the buffer pointed to by "s"
               needs to be at least "UTF8_MAXBYTES_CASE+1" bytes since the
               titlecase version may be longer than the original character.

               The first code point of the titlecased version is returned (but
               note, as explained at the top of this section, that there may
               be more).

                       UV      toTITLE_uvchr(UV cp, U8* s, STRLEN* lenp)

       toUPPER Converts the specified character to uppercase.  If the input is
               anything but an ASCII lowercase character, that input character
               itself is returned.  Variant "toUPPER_A" is equivalent.

                       U8      toUPPER(U8 ch)

       toUPPER_utf8
               This is like "toUPPER_utf8_safe", but doesn't have the "e"
               parameter  The function therefore can't check if it is reading
               beyond the end of the string.  Starting in Perl v5.30, it will
               take the "e" parameter, becoming a synonym for
               "toUPPER_utf8_safe".  At that time every program that uses it
               will have to be changed to successfully compile.  In the
               meantime, the first runtime call to "toUPPER_utf8" from each
               call point in the program will raise a deprecation warning,
               enabled by default.  You can convert your program now to use
               "toUPPER_utf8_safe", and avoid the warnings, and get an extra
               measure of protection, or you can wait until v5.30, when you'll
               be forced to add the "e" parameter.

                       UV      toUPPER_utf8(U8* p, U8* s, STRLEN* lenp)

       toUPPER_utf8_safe
               Converts the first UTF-8 encoded character in the sequence
               starting at "p" and extending no further than "e-1" to its
               uppercase version, and stores that in UTF-8 in "s", and its
               length in bytes in "lenp".  Note that the buffer pointed to by
               "s" needs to be at least "UTF8_MAXBYTES_CASE+1" bytes since the
               uppercase version may be longer than the original character.

               The first code point of the uppercased version is returned (but
               note, as explained at the top of this section, that there may
               be more).

               The suffix "_safe" in the function's name indicates that it
               will not attempt to read beyond "e-1", provided that the
               constraint "s<e" is true (this is asserted for in "-DDEBUGGING"
               builds).  If the UTF-8 for the input character is malformed in
               some way, the program may croak, or the function may return the
               REPLACEMENT CHARACTER, at the discretion of the implementation,
               and subject to change in future releases.

                       UV      toUPPER_utf8_safe(U8* p, U8* e, U8* s,
                                                 STRLEN* lenp)

       toUPPER_uvchr
               Converts the code point "cp" to its uppercase version, and
               stores that in UTF-8 in "s", and its length in bytes in "lenp".
               The code point is interpreted as native if less than 256;
               otherwise as Unicode.  Note that the buffer pointed to by "s"
               needs to be at least "UTF8_MAXBYTES_CASE+1" bytes since the
               uppercase version may be longer than the original character.

               The first code point of the uppercased version is returned (but
               note, as explained at the top of this section, that there may
               be more.)

                       UV      toUPPER_uvchr(UV cp, U8* s, STRLEN* lenp)

Character classification
       This section is about functions (really macros) that classify
       characters into types, such as punctuation versus alphabetic, etc.
       Most of these are analogous to regular expression character classes.
       (See "POSIX Character Classes" in perlrecharclass.)  There are several
       variants for each class.  (Not all macros have all variants; each item
       below lists the ones valid for it.)  None are affected by "use bytes",
       and only the ones with "LC" in the name are affected by the current
       locale.

       The base function, e.g., "isALPHA()", takes an octet (either a "char"
       or a "U8") as input and returns a boolean as to whether or not the
       character represented by that octet is (or on non-ASCII platforms,
       corresponds to) an ASCII character in the named class based on
       platform, Unicode, and Perl rules.  If the input is a number that
       doesn't fit in an octet, FALSE is returned.

       Variant "isFOO_A" (e.g., "isALPHA_A()") is identical to the base
       function with no suffix "_A".  This variant is used to emphasize by its
       name that only ASCII-range characters can return TRUE.

       Variant "isFOO_L1" imposes the Latin-1 (or EBCDIC equivalent) character
       set onto the platform.  That is, the code points that are ASCII are
       unaffected, since ASCII is a subset of Latin-1.  But the non-ASCII code
       points are treated as if they are Latin-1 characters.  For example,
       "isWORDCHAR_L1()" will return true when called with the code point
       0xDF, which is a word character in both ASCII and EBCDIC (though it
       represents different characters in each).

       Variant "isFOO_uvchr" is like the "isFOO_L1" variant, but accepts any
       UV code point as input.  If the code point is larger than 255, Unicode
       rules are used to determine if it is in the character class.  For
       example, "isWORDCHAR_uvchr(0x100)" returns TRUE, since 0x100 is LATIN
       CAPITAL LETTER A WITH MACRON in Unicode, and is a word character.

       Variant "isFOO_utf8_safe" is like "isFOO_uvchr", but is used for UTF-8
       encoded strings.  Each call classifies one character, even if the
       string contains many.  This variant takes two parameters.  The first,
       "p", is a pointer to the first byte of the character to be classified.
       (Recall that it may take more than one byte to represent a character in
       UTF-8 strings.)  The second parameter, "e", points to anywhere in the
       string beyond the first character, up to one byte past the end of the
       entire string.  The suffix "_safe" in the function's name indicates
       that it will not attempt to read beyond "e-1", provided that the
       constraint "s<e" is true (this is asserted for in "-DDEBUGGING"
       builds).  If the UTF-8 for the input character is malformed in some
       way, the program may croak, or the function may return FALSE, at the
       discretion of the implementation, and subject to change in future
       releases.

       Variant "isFOO_utf8" is like "isFOO_utf8_safe", but takes just a single
       parameter, "p", which has the same meaning as the corresponding
       parameter does in "isFOO_utf8_safe".  The function therefore can't
       check if it is reading beyond the end of the string.  Starting in Perl
       v5.30, it will take a second parameter, becoming a synonym for
       "isFOO_utf8_safe".  At that time every program that uses it will have
       to be changed to successfully compile.  In the meantime, the first
       runtime call to "isFOO_utf8" from each call point in the program will
       raise a deprecation warning, enabled by default.  You can convert your
       program now to use "isFOO_utf8_safe", and avoid the warnings, and get
       an extra measure of protection, or you can wait until v5.30, when
       you'll be forced to add the "e" parameter.

       Variant "isFOO_LC" is like the "isFOO_A" and "isFOO_L1" variants, but
       the result is based on the current locale, which is what "LC" in the
       name stands for.  If Perl can determine that the current locale is a
       UTF-8 locale, it uses the published Unicode rules; otherwise, it uses
       the C library function that gives the named classification.  For
       example, "isDIGIT_LC()" when not in a UTF-8 locale returns the result
       of calling "isdigit()".  FALSE is always returned if the input won't
       fit into an octet.  On some platforms where the C library function is
       known to be defective, Perl changes its result to follow the POSIX
       standard's rules.

       Variant "isFOO_LC_uvchr" is like "isFOO_LC", but is defined on any UV.
       It returns the same as "isFOO_LC" for input code points less than 256,
       and returns the hard-coded, not-affected-by-locale, Unicode results for
       larger ones.

       Variant "isFOO_LC_utf8_safe" is like "isFOO_LC_uvchr", but is used for
       UTF-8 encoded strings.  Each call classifies one character, even if the
       string contains many.  This variant takes two parameters.  The first,
       "p", is a pointer to the first byte of the character to be classified.
       (Recall that it may take more than one byte to represent a character in
       UTF-8 strings.) The second parameter, "e", points to anywhere in the
       string beyond the first character, up to one byte past the end of the
       entire string.  The suffix "_safe" in the function's name indicates
       that it will not attempt to read beyond "e-1", provided that the
       constraint "s<e" is true (this is asserted for in "-DDEBUGGING"
       builds).  If the UTF-8 for the input character is malformed in some
       way, the program may croak, or the function may return FALSE, at the
       discretion of the implementation, and subject to change in future
       releases.

       Variant "isFOO_LC_utf8" is like "isFOO_LC_utf8_safe", but takes just a
       single parameter, "p", which has the same meaning as the corresponding
       parameter does in "isFOO_LC_utf8_safe".  The function therefore can't
       check if it is reading beyond the end of the string.  Starting in Perl
       v5.30, it will take a second parameter, becoming a synonym for
       "isFOO_LC_utf8_safe".  At that time every program that uses it will
       have to be changed to successfully compile.  In the meantime, the first
       runtime call to "isFOO_LC_utf8" from each call point in the program
       will raise a deprecation warning, enabled by default.  You can convert
       your program now to use "isFOO_LC_utf8_safe", and avoid the warnings,
       and get an extra measure of protection, or you can wait until v5.30,
       when you'll be forced to add the "e" parameter.

       isALPHA Returns a boolean indicating whether the specified character is
               an alphabetic character, analogous to "m/[[:alpha:]]/".  See
               the top of this section for an explanation of variants
               "isALPHA_A", "isALPHA_L1", "isALPHA_uvchr",
               "isALPHA_utf8_safe", "isALPHA_LC", "isALPHA_LC_uvchr", and
               "isALPHA_LC_utf8_safe".

                       bool    isALPHA(char ch)

       isALPHANUMERIC
               Returns a boolean indicating whether the specified character is
               a either an alphabetic character or decimal digit, analogous to
               "m/[[:alnum:]]/".  See the top of this section for an
               explanation of variants "isALPHANUMERIC_A",
               "isALPHANUMERIC_L1", "isALPHANUMERIC_uvchr",
               "isALPHANUMERIC_utf8_safe", "isALPHANUMERIC_LC",
               "isALPHANUMERIC_LC_uvchr", and "isALPHANUMERIC_LC_utf8_safe".

                       bool    isALPHANUMERIC(char ch)

       isASCII Returns a boolean indicating whether the specified character is
               one of the 128 characters in the ASCII character set, analogous
               to "m/[[:ascii:]]/".  On non-ASCII platforms, it returns TRUE
               iff this character corresponds to an ASCII character.  Variants
               "isASCII_A()" and "isASCII_L1()" are identical to "isASCII()".
               See the top of this section for an explanation of variants
               "isASCII_uvchr", "isASCII_utf8_safe", "isASCII_LC",
               "isASCII_LC_uvchr", and "isASCII_LC_utf8_safe".  Note, however,
               that some platforms do not have the C library routine
               "isascii()".  In these cases, the variants whose names contain
               "LC" are the same as the corresponding ones without.

               Also note, that because all ASCII characters are UTF-8
               invariant (meaning they have the exact same representation
               (always a single byte) whether encoded in UTF-8 or not),
               "isASCII" will give the correct results when called with any
               byte in any string encoded or not in UTF-8.  And similarly
               "isASCII_utf8_safe" will work properly on any string encoded or
               not in UTF-8.

                       bool    isASCII(char ch)

       isBLANK Returns a boolean indicating whether the specified character is
               a character considered to be a blank, analogous to
               "m/[[:blank:]]/".  See the top of this section for an
               explanation of variants "isBLANK_A", "isBLANK_L1",
               "isBLANK_uvchr", "isBLANK_utf8_safe", "isBLANK_LC",
               "isBLANK_LC_uvchr", and "isBLANK_LC_utf8_safe".  Note, however,
               that some platforms do not have the C library routine
               "isblank()".  In these cases, the variants whose names contain
               "LC" are the same as the corresponding ones without.

                       bool    isBLANK(char ch)

       isCNTRL Returns a boolean indicating whether the specified character is
               a control character, analogous to "m/[[:cntrl:]]/".  See the
               top of this section for an explanation of variants "isCNTRL_A",
               "isCNTRL_L1", "isCNTRL_uvchr", "isCNTRL_utf8_safe",
               "isCNTRL_LC", "isCNTRL_LC_uvchr", and "isCNTRL_LC_utf8_safe" On
               EBCDIC platforms, you almost always want to use the
               "isCNTRL_L1" variant.

                       bool    isCNTRL(char ch)

       isDIGIT Returns a boolean indicating whether the specified character is
               a digit, analogous to "m/[[:digit:]]/".  Variants "isDIGIT_A"
               and "isDIGIT_L1" are identical to "isDIGIT".  See the top of
               this section for an explanation of variants "isDIGIT_uvchr",
               "isDIGIT_utf8_safe", "isDIGIT_LC", "isDIGIT_LC_uvchr", and
               "isDIGIT_LC_utf8_safe".

                       bool    isDIGIT(char ch)

       isGRAPH Returns a boolean indicating whether the specified character is
               a graphic character, analogous to "m/[[:graph:]]/".  See the
               top of this section for an explanation of variants "isGRAPH_A",
               "isGRAPH_L1", "isGRAPH_uvchr", "isGRAPH_utf8_safe",
               "isGRAPH_LC", "isGRAPH_LC_uvchr", and "isGRAPH_LC_utf8_safe".

                       bool    isGRAPH(char ch)

       isIDCONT
               Returns a boolean indicating whether the specified character
               can be the second or succeeding character of an identifier.
               This is very close to, but not quite the same as the official
               Unicode property "XID_Continue".  The difference is that this
               returns true only if the input character also matches
               "isWORDCHAR".  See the top of this section for an explanation
               of variants "isIDCONT_A", "isIDCONT_L1", "isIDCONT_uvchr",
               "isIDCONT_utf8_safe", "isIDCONT_LC", "isIDCONT_LC_uvchr", and
               "isIDCONT_LC_utf8_safe".

                       bool    isIDCONT(char ch)

       isIDFIRST
               Returns a boolean indicating whether the specified character
               can be the first character of an identifier.  This is very
               close to, but not quite the same as the official Unicode
               property "XID_Start".  The difference is that this returns true
               only if the input character also matches "isWORDCHAR".  See the
               top of this section for an explanation of variants
               "isIDFIRST_A", "isIDFIRST_L1", "isIDFIRST_uvchr",
               "isIDFIRST_utf8_safe", "isIDFIRST_LC", "isIDFIRST_LC_uvchr",
               and "isIDFIRST_LC_utf8_safe".

                       bool    isIDFIRST(char ch)

       isLOWER Returns a boolean indicating whether the specified character is
               a lowercase character, analogous to "m/[[:lower:]]/".  See the
               top of this section for an explanation of variants "isLOWER_A",
               "isLOWER_L1", "isLOWER_uvchr", "isLOWER_utf8_safe",
               "isLOWER_LC", "isLOWER_LC_uvchr", and "isLOWER_LC_utf8_safe".

                       bool    isLOWER(char ch)

       isOCTAL Returns a boolean indicating whether the specified character is
               an octal digit, [0-7].  The only two variants are "isOCTAL_A"
               and "isOCTAL_L1"; each is identical to "isOCTAL".

                       bool    isOCTAL(char ch)

       isPRINT Returns a boolean indicating whether the specified character is
               a printable character, analogous to "m/[[:print:]]/".  See the
               top of this section for an explanation of variants "isPRINT_A",
               "isPRINT_L1", "isPRINT_uvchr", "isPRINT_utf8_safe",
               "isPRINT_LC", "isPRINT_LC_uvchr", and "isPRINT_LC_utf8_safe".

                       bool    isPRINT(char ch)

       isPSXSPC
               (short for Posix Space) Starting in 5.18, this is identical in
               all its forms to the corresponding "isSPACE()" macros.  The
               locale forms of this macro are identical to their corresponding
               "isSPACE()" forms in all Perl releases.  In releases prior to
               5.18, the non-locale forms differ from their "isSPACE()" forms
               only in that the "isSPACE()" forms don't match a Vertical Tab,
               and the "isPSXSPC()" forms do.  Otherwise they are identical.
               Thus this macro is analogous to what "m/[[:space:]]/" matches
               in a regular expression.  See the top of this section for an
               explanation of variants "isPSXSPC_A", "isPSXSPC_L1",
               "isPSXSPC_uvchr", "isPSXSPC_utf8_safe", "isPSXSPC_LC",
               "isPSXSPC_LC_uvchr", and "isPSXSPC_LC_utf8_safe".

                       bool    isPSXSPC(char ch)

       isPUNCT Returns a boolean indicating whether the specified character is
               a punctuation character, analogous to "m/[[:punct:]]/".  Note
               that the definition of what is punctuation isn't as
               straightforward as one might desire.  See "POSIX Character
               Classes" in perlrecharclass for details.  See the top of this
               section for an explanation of variants "isPUNCT_A",
               "isPUNCT_L1", "isPUNCT_uvchr", "isPUNCT_utf8_safe",
               "isPUNCT_LC", "isPUNCT_LC_uvchr", and "isPUNCT_LC_utf8_safe".

                       bool    isPUNCT(char ch)

       isSPACE Returns a boolean indicating whether the specified character is
               a whitespace character.  This is analogous to what "m/\s/"
               matches in a regular expression.  Starting in Perl 5.18 this
               also matches what "m/[[:space:]]/" does.  Prior to 5.18, only
               the locale forms of this macro (the ones with "LC" in their
               names) matched precisely what "m/[[:space:]]/" does.  In those
               releases, the only difference, in the non-locale variants, was
               that "isSPACE()" did not match a vertical tab.  (See "isPSXSPC"
               for a macro that matches a vertical tab in all releases.)  See
               the top of this section for an explanation of variants
               "isSPACE_A", "isSPACE_L1", "isSPACE_uvchr",
               "isSPACE_utf8_safe", "isSPACE_LC", "isSPACE_LC_uvchr", and
               "isSPACE_LC_utf8_safe".

                       bool    isSPACE(char ch)

       isUPPER Returns a boolean indicating whether the specified character is
               an uppercase character, analogous to "m/[[:upper:]]/".  See the
               top of this section for an explanation of variants "isUPPER_A",
               "isUPPER_L1", "isUPPER_uvchr", "isUPPER_utf8_safe",
               "isUPPER_LC", "isUPPER_LC_uvchr", and "isUPPER_LC_utf8_safe".

                       bool    isUPPER(char ch)

       isWORDCHAR
               Returns a boolean indicating whether the specified character is
               a character that is a word character, analogous to what "m/\w/"
               and "m/[[:word:]]/" match in a regular expression.  A word
               character is an alphabetic character, a decimal digit, a
               connecting punctuation character (such as an underscore), or a
               "mark" character that attaches to one of those (like some sort
               of accent).  "isALNUM()" is a synonym provided for backward
               compatibility, even though a word character includes more than
               the standard C language meaning of alphanumeric.  See the top
               of this section for an explanation of variants "isWORDCHAR_A",
               "isWORDCHAR_L1", "isWORDCHAR_uvchr", and
               "isWORDCHAR_utf8_safe".  "isWORDCHAR_LC",
               "isWORDCHAR_LC_uvchr", and "isWORDCHAR_LC_utf8_safe" are also
               as described there, but additionally include the platform's
               native underscore.

                       bool    isWORDCHAR(char ch)

       isXDIGIT
               Returns a boolean indicating whether the specified character is
               a hexadecimal digit.  In the ASCII range these are
               "[0-9A-Fa-f]".  Variants "isXDIGIT_A()" and "isXDIGIT_L1()" are
               identical to "isXDIGIT()".  See the top of this section for an
               explanation of variants "isXDIGIT_uvchr", "isXDIGIT_utf8_safe",
               "isXDIGIT_LC", "isXDIGIT_LC_uvchr", and
               "isXDIGIT_LC_utf8_safe".

                       bool    isXDIGIT(char ch)

Cloning an interpreter
       perl_clone
               Create and return a new interpreter by cloning the current one.

               "perl_clone" takes these flags as parameters:

               "CLONEf_COPY_STACKS" - is used to, well, copy the stacks also,
               without it we only clone the data and zero the stacks, with it
               we copy the stacks and the new perl interpreter is ready to run
               at the exact same point as the previous one.  The pseudo-fork
               code uses "COPY_STACKS" while the threads->create doesn't.

               "CLONEf_KEEP_PTR_TABLE" - "perl_clone" keeps a ptr_table with
               the pointer of the old variable as a key and the new variable
               as a value, this allows it to check if something has been
               cloned and not clone it again but rather just use the value and
               increase the refcount.  If "KEEP_PTR_TABLE" is not set then
               "perl_clone" will kill the ptr_table using the function
               "ptr_table_free(PL_ptr_table); PL_ptr_table = NULL;", reason to
               keep it around is if you want to dup some of your own variable
               who are outside the graph perl scans, an example of this code
               is in threads.xs create.

               "CLONEf_CLONE_HOST" - This is a win32 thing, it is ignored on
               unix, it tells perls win32host code (which is c++) to clone
               itself, this is needed on win32 if you want to run two threads
               at the same time, if you just want to do some stuff in a
               separate perl interpreter and then throw it away and return to
               the original one, you don't need to do anything.

                       PerlInterpreter* perl_clone(
                                            PerlInterpreter *proto_perl,
                                            UV flags
                                        )

Compile-time scope hooks
       BhkDISABLE
               NOTE: this function is experimental and may change or be
               removed without notice.

               Temporarily disable an entry in this BHK structure, by clearing
               the appropriate flag.  "which" is a preprocessor token
               indicating which entry to disable.

                       void    BhkDISABLE(BHK *hk, which)

       BhkENABLE
               NOTE: this function is experimental and may change or be
               removed without notice.

               Re-enable an entry in this BHK structure, by setting the
               appropriate flag.  "which" is a preprocessor token indicating
               which entry to enable.  This will assert (under -DDEBUGGING) if
               the entry doesn't contain a valid pointer.

                       void    BhkENABLE(BHK *hk, which)

       BhkENTRY_set
               NOTE: this function is experimental and may change or be
               removed without notice.

               Set an entry in the BHK structure, and set the flags to
               indicate it is valid.  "which" is a preprocessing token
               indicating which entry to set.  The type of "ptr" depends on
               the entry.

                       void    BhkENTRY_set(BHK *hk, which, void *ptr)

       blockhook_register
               NOTE: this function is experimental and may change or be
               removed without notice.

               Register a set of hooks to be called when the Perl lexical
               scope changes at compile time.  See "Compile-time scope hooks"
               in perlguts.

               NOTE: this function must be explicitly called as
               Perl_blockhook_register with an aTHX_ parameter.

                       void    Perl_blockhook_register(pTHX_ BHK *hk)

COP Hint Hashes
       cophh_2hv
               NOTE: this function is experimental and may change or be
               removed without notice.

               Generates and returns a standard Perl hash representing the
               full set of key/value pairs in the cop hints hash "cophh".
               "flags" is currently unused and must be zero.

                       HV *    cophh_2hv(const COPHH *cophh, U32 flags)

       cophh_copy
               NOTE: this function is experimental and may change or be
               removed without notice.

               Make and return a complete copy of the cop hints hash "cophh".

                       COPHH * cophh_copy(COPHH *cophh)

       cophh_delete_pv
               NOTE: this function is experimental and may change or be
               removed without notice.

               Like "cophh_delete_pvn", but takes a nul-terminated string
               instead of a string/length pair.

                       COPHH * cophh_delete_pv(const COPHH *cophh,
                                               const char *key, U32 hash,
                                               U32 flags)

       cophh_delete_pvn
               NOTE: this function is experimental and may change or be
               removed without notice.

               Delete a key and its associated value from the cop hints hash
               "cophh", and returns the modified hash.  The returned hash
               pointer is in general not the same as the hash pointer that was
               passed in.  The input hash is consumed by the function, and the
               pointer to it must not be subsequently used.  Use "cophh_copy"
               if you need both hashes.

               The key is specified by "keypv" and "keylen".  If "flags" has
               the "COPHH_KEY_UTF8" bit set, the key octets are interpreted as
               UTF-8, otherwise they are interpreted as Latin-1.  "hash" is a
               precomputed hash of the key string, or zero if it has not been
               precomputed.

                       COPHH * cophh_delete_pvn(COPHH *cophh,
                                                const char *keypv,
                                                STRLEN keylen, U32 hash,
                                                U32 flags)

       cophh_delete_pvs
               NOTE: this function is experimental and may change or be
               removed without notice.

               Like "cophh_delete_pvn", but takes a literal string instead of
               a string/length pair, and no precomputed hash.

                       COPHH * cophh_delete_pvs(const COPHH *cophh,
                                                "literal string" key,
                                                U32 flags)

       cophh_delete_sv
               NOTE: this function is experimental and may change or be
               removed without notice.

               Like "cophh_delete_pvn", but takes a Perl scalar instead of a
               string/length pair.

                       COPHH * cophh_delete_sv(const COPHH *cophh, SV *key,
                                               U32 hash, U32 flags)

       cophh_fetch_pv
               NOTE: this function is experimental and may change or be
               removed without notice.

               Like "cophh_fetch_pvn", but takes a nul-terminated string
               instead of a string/length pair.

                       SV *    cophh_fetch_pv(const COPHH *cophh,
                                              const char *key, U32 hash,
                                              U32 flags)

       cophh_fetch_pvn
               NOTE: this function is experimental and may change or be
               removed without notice.

               Look up the entry in the cop hints hash "cophh" with the key
               specified by "keypv" and "keylen".  If "flags" has the
               "COPHH_KEY_UTF8" bit set, the key octets are interpreted as
               UTF-8, otherwise they are interpreted as Latin-1.  "hash" is a
               precomputed hash of the key string, or zero if it has not been
               precomputed.  Returns a mortal scalar copy of the value
               associated with the key, or &PL_sv_placeholder if there is no
               value associated with the key.

                       SV *    cophh_fetch_pvn(const COPHH *cophh,
                                               const char *keypv,
                                               STRLEN keylen, U32 hash,
                                               U32 flags)

       cophh_fetch_pvs
               NOTE: this function is experimental and may change or be
               removed without notice.

               Like "cophh_fetch_pvn", but takes a literal string instead of a
               string/length pair, and no precomputed hash.

                       SV *    cophh_fetch_pvs(const COPHH *cophh,
                                               "literal string" key, U32 flags)

       cophh_fetch_sv
               NOTE: this function is experimental and may change or be
               removed without notice.

               Like "cophh_fetch_pvn", but takes a Perl scalar instead of a
               string/length pair.

                       SV *    cophh_fetch_sv(const COPHH *cophh, SV *key,
                                              U32 hash, U32 flags)

       cophh_free
               NOTE: this function is experimental and may change or be
               removed without notice.

               Discard the cop hints hash "cophh", freeing all resources
               associated with it.

                       void    cophh_free(COPHH *cophh)

       cophh_new_empty
               NOTE: this function is experimental and may change or be
               removed without notice.

               Generate and return a fresh cop hints hash containing no
               entries.

                       COPHH * cophh_new_empty()

       cophh_store_pv
               NOTE: this function is experimental and may change or be
               removed without notice.

               Like "cophh_store_pvn", but takes a nul-terminated string
               instead of a string/length pair.

                       COPHH * cophh_store_pv(const COPHH *cophh,
                                              const char *key, U32 hash,
                                              SV *value, U32 flags)

       cophh_store_pvn
               NOTE: this function is experimental and may change or be
               removed without notice.

               Stores a value, associated with a key, in the cop hints hash
               "cophh", and returns the modified hash.  The returned hash
               pointer is in general not the same as the hash pointer that was
               passed in.  The input hash is consumed by the function, and the
               pointer to it must not be subsequently used.  Use "cophh_copy"
               if you need both hashes.

               The key is specified by "keypv" and "keylen".  If "flags" has
               the "COPHH_KEY_UTF8" bit set, the key octets are interpreted as
               UTF-8, otherwise they are interpreted as Latin-1.  "hash" is a
               precomputed hash of the key string, or zero if it has not been
               precomputed.

               "value" is the scalar value to store for this key.  "value" is
               copied by this function, which thus does not take ownership of
               any reference to it, and later changes to the scalar will not
               be reflected in the value visible in the cop hints hash.
               Complex types of scalar will not be stored with referential
               integrity, but will be coerced to strings.

                       COPHH * cophh_store_pvn(COPHH *cophh, const char *keypv,
                                               STRLEN keylen, U32 hash,
                                               SV *value, U32 flags)

       cophh_store_pvs
               NOTE: this function is experimental and may change or be
               removed without notice.

               Like "cophh_store_pvn", but takes a literal string instead of a
               string/length pair, and no precomputed hash.

                       COPHH * cophh_store_pvs(const COPHH *cophh,
                                               "literal string" key, SV *value,
                                               U32 flags)

       cophh_store_sv
               NOTE: this function is experimental and may change or be
               removed without notice.

               Like "cophh_store_pvn", but takes a Perl scalar instead of a
               string/length pair.

                       COPHH * cophh_store_sv(const COPHH *cophh, SV *key,
                                              U32 hash, SV *value, U32 flags)

COP Hint Reading
       cop_hints_2hv
               Generates and returns a standard Perl hash representing the
               full set of hint entries in the cop "cop".  "flags" is
               currently unused and must be zero.

                       HV *    cop_hints_2hv(const COP *cop, U32 flags)

       cop_hints_fetch_pv
               Like "cop_hints_fetch_pvn", but takes a nul-terminated string
               instead of a string/length pair.

                       SV *    cop_hints_fetch_pv(const COP *cop,
                                                  const char *key, U32 hash,
                                                  U32 flags)

       cop_hints_fetch_pvn
               Look up the hint entry in the cop "cop" with the key specified
               by "keypv" and "keylen".  If "flags" has the "COPHH_KEY_UTF8"
               bit set, the key octets are interpreted as UTF-8, otherwise
               they are interpreted as Latin-1.  "hash" is a precomputed hash
               of the key string, or zero if it has not been precomputed.
               Returns a mortal scalar copy of the value associated with the
               key, or &PL_sv_placeholder if there is no value associated with
               the key.

                       SV *    cop_hints_fetch_pvn(const COP *cop,
                                                   const char *keypv,
                                                   STRLEN keylen, U32 hash,
                                                   U32 flags)

       cop_hints_fetch_pvs
               Like "cop_hints_fetch_pvn", but takes a literal string instead
               of a string/length pair, and no precomputed hash.

                       SV *    cop_hints_fetch_pvs(const COP *cop,
                                                   "literal string" key,
                                                   U32 flags)

       cop_hints_fetch_sv
               Like "cop_hints_fetch_pvn", but takes a Perl scalar instead of
               a string/length pair.

                       SV *    cop_hints_fetch_sv(const COP *cop, SV *key,
                                                  U32 hash, U32 flags)

Custom Operators
       custom_op_register
               Register a custom op.  See "Custom Operators" in perlguts.

               NOTE: this function must be explicitly called as
               Perl_custom_op_register with an aTHX_ parameter.

                       void    Perl_custom_op_register(pTHX_
                                                       Perl_ppaddr_t ppaddr,
                                                       const XOP *xop)

       custom_op_xop
               Return the XOP structure for a given custom op.  This macro
               should be considered internal to "OP_NAME" and the other access
               macros: use them instead.  This macro does call a function.
               Prior to 5.19.6, this was implemented as a function.

               NOTE: this function must be explicitly called as
               Perl_custom_op_xop with an aTHX_ parameter.

                       const XOP * Perl_custom_op_xop(pTHX_ const OP *o)

       XopDISABLE
               Temporarily disable a member of the XOP, by clearing the
               appropriate flag.

                       void    XopDISABLE(XOP *xop, which)

       XopENABLE
               Reenable a member of the XOP which has been disabled.

                       void    XopENABLE(XOP *xop, which)

       XopENTRY
               Return a member of the XOP structure.  "which" is a cpp token
               indicating which entry to return.  If the member is not set
               this will return a default value.  The return type depends on
               "which".  This macro evaluates its arguments more than once.
               If you are using "Perl_custom_op_xop" to retreive a "XOP *"
               from a "OP *", use the more efficient "XopENTRYCUSTOM" instead.

                               XopENTRY(XOP *xop, which)

       XopENTRYCUSTOM
               Exactly like "XopENTRY(XopENTRY(Perl_custom_op_xop(aTHX_ o),
               which)" but more efficient.  The "which" parameter is identical
               to "XopENTRY".

                               XopENTRYCUSTOM(const OP *o, which)

       XopENTRY_set
               Set a member of the XOP structure.  "which" is a cpp token
               indicating which entry to set.  See "Custom Operators" in
               perlguts for details about the available members and how they
               are used.  This macro evaluates its argument more than once.

                       void    XopENTRY_set(XOP *xop, which, value)

       XopFLAGS
               Return the XOP's flags.

                       U32     XopFLAGS(XOP *xop)

CV Manipulation Functions
       This section documents functions to manipulate CVs which are code-
       values, or subroutines.  For more information, see perlguts.

       caller_cx
               The XSUB-writer's equivalent of caller().  The returned
               "PERL_CONTEXT" structure can be interrogated to find all the
               information returned to Perl by "caller".  Note that XSUBs
               don't get a stack frame, so "caller_cx(0, NULL)" will return
               information for the immediately-surrounding Perl code.

               This function skips over the automatic calls to &DB::sub made
               on the behalf of the debugger.  If the stack frame requested
               was a sub called by "DB::sub", the return value will be the
               frame for the call to "DB::sub", since that has the correct
               line number/etc. for the call site.  If dbcxp is non-"NULL", it
               will be set to a pointer to the frame for the sub call itself.

                       const PERL_CONTEXT * caller_cx(
                                                I32 level,
                                                const PERL_CONTEXT **dbcxp
                                            )

       CvSTASH Returns the stash of the CV.  A stash is the symbol table hash,
               containing the package-scoped variables in the package where
               the subroutine was defined.  For more information, see
               perlguts.

               This also has a special use with XS AUTOLOAD subs.  See
               "Autoloading with XSUBs" in perlguts.

                       HV*     CvSTASH(CV* cv)

       find_runcv
               Locate the CV corresponding to the currently executing sub or
               eval.  If "db_seqp" is non_null, skip CVs that are in the DB
               package and populate *db_seqp with the cop sequence number at
               the point that the DB:: code was entered.  (This allows
               debuggers to eval in the scope of the breakpoint rather than in
               the scope of the debugger itself.)

                       CV*     find_runcv(U32 *db_seqp)

       get_cv  Uses "strlen" to get the length of "name", then calls
               "get_cvn_flags".

               NOTE: the perl_ form of this function is deprecated.

                       CV*     get_cv(const char* name, I32 flags)

       get_cvn_flags
               Returns the CV of the specified Perl subroutine.  "flags" are
               passed to "gv_fetchpvn_flags".  If "GV_ADD" is set and the Perl
               subroutine does not exist then it will be declared (which has
               the same effect as saying "sub name;").  If "GV_ADD" is not set
               and the subroutine does not exist then NULL is returned.

               NOTE: the perl_ form of this function is deprecated.

                       CV*     get_cvn_flags(const char* name, STRLEN len,
                                             I32 flags)

"xsubpp" variables and internal functions
       ax      Variable which is setup by "xsubpp" to indicate the stack base
               offset, used by the "ST", "XSprePUSH" and "XSRETURN" macros.
               The "dMARK" macro must be called prior to setup the "MARK"
               variable.

                       I32     ax

       CLASS   Variable which is setup by "xsubpp" to indicate the class name
               for a C++ XS constructor.  This is always a "char*".  See
               "THIS".

                       char*   CLASS

       dAX     Sets up the "ax" variable.  This is usually handled
               automatically by "xsubpp" by calling "dXSARGS".

                               dAX;

       dAXMARK Sets up the "ax" variable and stack marker variable "mark".
               This is usually handled automatically by "xsubpp" by calling
               "dXSARGS".

                               dAXMARK;

       dITEMS  Sets up the "items" variable.  This is usually handled
               automatically by "xsubpp" by calling "dXSARGS".

                               dITEMS;

       dUNDERBAR
               Sets up any variable needed by the "UNDERBAR" macro.  It used
               to define "padoff_du", but it is currently a noop.  However, it
               is strongly advised to still use it for ensuring past and
               future compatibility.

                               dUNDERBAR;

       dXSARGS Sets up stack and mark pointers for an XSUB, calling "dSP" and
               "dMARK".  Sets up the "ax" and "items" variables by calling
               "dAX" and "dITEMS".  This is usually handled automatically by
               "xsubpp".

                               dXSARGS;

       dXSI32  Sets up the "ix" variable for an XSUB which has aliases.  This
               is usually handled automatically by "xsubpp".

                               dXSI32;

       items   Variable which is setup by "xsubpp" to indicate the number of
               items on the stack.  See "Variable-length Parameter Lists" in
               perlxs.

                       I32     items

       ix      Variable which is setup by "xsubpp" to indicate which of an
               XSUB's aliases was used to invoke it.  See "The ALIAS: Keyword"
               in perlxs.

                       I32     ix

       RETVAL  Variable which is setup by "xsubpp" to hold the return value
               for an XSUB.  This is always the proper type for the XSUB.  See
               "The RETVAL Variable" in perlxs.

                       (whatever)      RETVAL

       ST      Used to access elements on the XSUB's stack.

                       SV*     ST(int ix)

       THIS    Variable which is setup by "xsubpp" to designate the object in
               a C++ XSUB.  This is always the proper type for the C++ object.
               See "CLASS" and "Using XS With C++" in perlxs.

                       (whatever)      THIS

       UNDERBAR
               The SV* corresponding to the $_ variable.  Works even if there
               is a lexical $_ in scope.

       XS      Macro to declare an XSUB and its C parameter list.  This is
               handled by "xsubpp".  It is the same as using the more explicit
               "XS_EXTERNAL" macro.

       XS_EXTERNAL
               Macro to declare an XSUB and its C parameter list explicitly
               exporting the symbols.

       XS_INTERNAL
               Macro to declare an XSUB and its C parameter list without
               exporting the symbols.  This is handled by "xsubpp" and
               generally preferable over exporting the XSUB symbols
               unnecessarily.

Debugging Utilities
       dump_all
               Dumps the entire optree of the current program starting at
               "PL_main_root" to "STDERR".  Also dumps the optrees for all
               visible subroutines in "PL_defstash".

                       void    dump_all()

       dump_packsubs
               Dumps the optrees for all visible subroutines in "stash".

                       void    dump_packsubs(const HV* stash)

       op_class
               Given an op, determine what type of struct it has been
               allocated as.  Returns one of the OPclass enums, such as
               OPclass_LISTOP.

                       OPclass op_class(const OP *o)

       op_dump Dumps the optree starting at OP "o" to "STDERR".

                       void    op_dump(const OP *o)

       sv_dump Dumps the contents of an SV to the "STDERR" filehandle.

               For an example of its output, see Devel::Peek.

                       void    sv_dump(SV* sv)

Display and Dump functions
       pv_display
               Similar to

                 pv_escape(dsv,pv,cur,pvlim,PERL_PV_ESCAPE_QUOTE);

               except that an additional "\0" will be appended to the string
               when len > cur and pv[cur] is "\0".

               Note that the final string may be up to 7 chars longer than
               pvlim.

                       char*   pv_display(SV *dsv, const char *pv, STRLEN cur,
                                          STRLEN len, STRLEN pvlim)

       pv_escape
               Escapes at most the first "count" chars of "pv" and puts the
               results into "dsv" such that the size of the escaped string
               will not exceed "max" chars and will not contain any incomplete
               escape sequences.  The number of bytes escaped will be returned
               in the "STRLEN *escaped" parameter if it is not null.  When the
               "dsv" parameter is null no escaping actually occurs, but the
               number of bytes that would be escaped were it not null will be
               calculated.

               If flags contains "PERL_PV_ESCAPE_QUOTE" then any double quotes
               in the string will also be escaped.

               Normally the SV will be cleared before the escaped string is
               prepared, but when "PERL_PV_ESCAPE_NOCLEAR" is set this will
               not occur.

               If "PERL_PV_ESCAPE_UNI" is set then the input string is treated
               as UTF-8 if "PERL_PV_ESCAPE_UNI_DETECT" is set then the input
               string is scanned using "is_utf8_string()" to determine if it
               is UTF-8.

               If "PERL_PV_ESCAPE_ALL" is set then all input chars will be
               output using "\x01F1" style escapes, otherwise if
               "PERL_PV_ESCAPE_NONASCII" is set, only non-ASCII chars will be
               escaped using this style; otherwise, only chars above 255 will
               be so escaped; other non printable chars will use octal or
               common escaped patterns like "\n".  Otherwise, if
               "PERL_PV_ESCAPE_NOBACKSLASH" then all chars below 255 will be
               treated as printable and will be output as literals.

               If "PERL_PV_ESCAPE_FIRSTCHAR" is set then only the first char
               of the string will be escaped, regardless of max.  If the
               output is to be in hex, then it will be returned as a plain hex
               sequence.  Thus the output will either be a single char, an
               octal escape sequence, a special escape like "\n" or a hex
               value.

               If "PERL_PV_ESCAPE_RE" is set then the escape char used will be
               a "%" and not a "\\".  This is because regexes very often
               contain backslashed sequences, whereas "%" is not a
               particularly common character in patterns.

               Returns a pointer to the escaped text as held by "dsv".

                       char*   pv_escape(SV *dsv, char const * const str,
                                         const STRLEN count, const STRLEN max,
                                         STRLEN * const escaped,
                                         const U32 flags)

       pv_pretty
               Converts a string into something presentable, handling escaping
               via "pv_escape()" and supporting quoting and ellipses.

               If the "PERL_PV_PRETTY_QUOTE" flag is set then the result will
               be double quoted with any double quotes in the string escaped.
               Otherwise if the "PERL_PV_PRETTY_LTGT" flag is set then the
               result be wrapped in angle brackets.

               If the "PERL_PV_PRETTY_ELLIPSES" flag is set and not all
               characters in string were output then an ellipsis "..." will be
               appended to the string.  Note that this happens AFTER it has
               been quoted.

               If "start_color" is non-null then it will be inserted after the
               opening quote (if there is one) but before the escaped text.
               If "end_color" is non-null then it will be inserted after the
               escaped text but before any quotes or ellipses.

               Returns a pointer to the prettified text as held by "dsv".

                       char*   pv_pretty(SV *dsv, char const * const str,
                                         const STRLEN count, const STRLEN max,
                                         char const * const start_color,
                                         char const * const end_color,
                                         const U32 flags)

Embedding Functions
       cv_clone
               Clone a CV, making a lexical closure.  "proto" supplies the
               prototype of the function: its code, pad structure, and other
               attributes.  The prototype is combined with a capture of outer
               lexicals to which the code refers, which are taken from the
               currently-executing instance of the immediately surrounding
               code.

                       CV *    cv_clone(CV *proto)

       cv_name Returns an SV containing the name of the CV, mainly for use in
               error reporting.  The CV may actually be a GV instead, in which
               case the returned SV holds the GV's name.  Anything other than
               a GV or CV is treated as a string already holding the sub name,
               but this could change in the future.

               An SV may be passed as a second argument.  If so, the name will
               be assigned to it and it will be returned.  Otherwise the
               returned SV will be a new mortal.

               If "flags" has the "CV_NAME_NOTQUAL" bit set, then the package
               name will not be included.  If the first argument is neither a
               CV nor a GV, this flag is ignored (subject to change).

                       SV *    cv_name(CV *cv, SV *sv, U32 flags)

       cv_undef
               Clear out all the active components of a CV.  This can happen
               either by an explicit "undef &foo", or by the reference count
               going to zero.  In the former case, we keep the "CvOUTSIDE"
               pointer, so that any anonymous children can still follow the
               full lexical scope chain.

                       void    cv_undef(CV* cv)

       find_rundefsv
               Returns the global variable $_.

                       SV *    find_rundefsv()

       find_rundefsvoffset
               DEPRECATED!  It is planned to remove this function from a
               future release of Perl.  Do not use it for new code; remove it
               from existing code.

               Until the lexical $_ feature was removed, this function would
               find the position of the lexical $_ in the pad of the
               currently-executing function and return the offset in the
               current pad, or "NOT_IN_PAD".

               Now it always returns "NOT_IN_PAD".

               NOTE: the perl_ form of this function is deprecated.

                       PADOFFSET find_rundefsvoffset()

       intro_my
               "Introduce" "my" variables to visible status.  This is called
               during parsing at the end of each statement to make lexical
               variables visible to subsequent statements.

                       U32     intro_my()

       load_module
               Loads the module whose name is pointed to by the string part of
               "name".  Note that the actual module name, not its filename,
               should be given.  Eg, "Foo::Bar" instead of "Foo/Bar.pm". ver,
               if specified and not NULL, provides version semantics similar
               to "use Foo::Bar VERSION". The optional trailing arguments can
               be used to specify arguments to the module's "import()" method,
               similar to "use Foo::Bar VERSION LIST"; their precise handling
               depends on the flags. The flags argument is a bitwise-ORed
               collection of any of "PERL_LOADMOD_DENY",
               "PERL_LOADMOD_NOIMPORT", or "PERL_LOADMOD_IMPORT_OPS" (or 0 for
               no flags).

               If "PERL_LOADMOD_NOIMPORT" is set, the module is loaded as if
               with an empty import list, as in "use Foo::Bar ()"; this is the
               only circumstance in which the trailing optional arguments may
               be omitted entirely. Otherwise, if "PERL_LOADMOD_IMPORT_OPS" is
               set, the trailing arguments must consist of exactly one "OP*",
               containing the op tree that produces the relevant import
               arguments. Otherwise, the trailing arguments must all be "SV*"
               values that will be used as import arguments; and the list must
               be terminated with "(SV*) NULL". If neither
               "PERL_LOADMOD_NOIMPORT" nor "PERL_LOADMOD_IMPORT_OPS" is set,
               the trailing "NULL" pointer is needed even if no import
               arguments are desired. The reference count for each specified
               "SV*" argument is decremented. In addition, the "name" argument
               is modified.

               If "PERL_LOADMOD_DENY" is set, the module is loaded as if with
               "no" rather than "use".

                       void    load_module(U32 flags, SV* name, SV* ver, ...)

       newPADNAMELIST
               NOTE: this function is experimental and may change or be
               removed without notice.

               Creates a new pad name list.  "max" is the highest index for
               which space is allocated.

                       PADNAMELIST * newPADNAMELIST(size_t max)

       newPADNAMEouter
               NOTE: this function is experimental and may change or be
               removed without notice.

               Constructs and returns a new pad name.  Only use this function
               for names that refer to outer lexicals.  (See also
               "newPADNAMEpvn".)  "outer" is the outer pad name that this one
               mirrors.  The returned pad name has the "PADNAMEt_OUTER" flag
               already set.

                       PADNAME * newPADNAMEouter(PADNAME *outer)

       newPADNAMEpvn
               NOTE: this function is experimental and may change or be
               removed without notice.

               Constructs and returns a new pad name.  "s" must be a UTF-8
               string.  Do not use this for pad names that point to outer
               lexicals.  See "newPADNAMEouter".

                       PADNAME * newPADNAMEpvn(const char *s, STRLEN len)

       nothreadhook
               Stub that provides thread hook for perl_destruct when there are
               no threads.

                       int     nothreadhook()

       pad_add_anon
               Allocates a place in the currently-compiling pad (via
               "pad_alloc") for an anonymous function that is lexically scoped
               inside the currently-compiling function.  The function "func"
               is linked into the pad, and its "CvOUTSIDE" link to the outer
               scope is weakened to avoid a reference loop.

               One reference count is stolen, so you may need to do
               "SvREFCNT_inc(func)".

               "optype" should be an opcode indicating the type of operation
               that the pad entry is to support.  This doesn't affect
               operational semantics, but is used for debugging.

                       PADOFFSET pad_add_anon(CV *func, I32 optype)

       pad_add_name_pv
               Exactly like "pad_add_name_pvn", but takes a nul-terminated
               string instead of a string/length pair.

                       PADOFFSET pad_add_name_pv(const char *name, U32 flags,
                                                 HV *typestash, HV *ourstash)

       pad_add_name_pvn
               Allocates a place in the currently-compiling pad for a named
               lexical variable.  Stores the name and other metadata in the
               name part of the pad, and makes preparations to manage the
               variable's lexical scoping.  Returns the offset of the
               allocated pad slot.

               "namepv"/"namelen" specify the variable's name, including
               leading sigil.  If "typestash" is non-null, the name is for a
               typed lexical, and this identifies the type.  If "ourstash" is
               non-null, it's a lexical reference to a package variable, and
               this identifies the package.  The following flags can be OR'ed
               together:

                padadd_OUR          redundantly specifies if it's a package var
                padadd_STATE        variable will retain value persistently
                padadd_NO_DUP_CHECK skip check for lexical shadowing

                       PADOFFSET pad_add_name_pvn(const char *namepv,
                                                  STRLEN namelen, U32 flags,
                                                  HV *typestash, HV *ourstash)

       pad_add_name_sv
               Exactly like "pad_add_name_pvn", but takes the name string in
               the form of an SV instead of a string/length pair.

                       PADOFFSET pad_add_name_sv(SV *name, U32 flags,
                                                 HV *typestash, HV *ourstash)

       pad_alloc
               NOTE: this function is experimental and may change or be
               removed without notice.

               Allocates a place in the currently-compiling pad, returning the
               offset of the allocated pad slot.  No name is initially
               attached to the pad slot.  "tmptype" is a set of flags
               indicating the kind of pad entry required, which will be set in
               the value SV for the allocated pad entry:

                   SVs_PADMY    named lexical variable ("my", "our", "state")
                   SVs_PADTMP   unnamed temporary store
                   SVf_READONLY constant shared between recursion levels

               "SVf_READONLY" has been supported here only since perl 5.20.
               To work with earlier versions as well, use
               "SVf_READONLY|SVs_PADTMP".  "SVf_READONLY" does not cause the
               SV in the pad slot to be marked read-only, but simply tells
               "pad_alloc" that it will be made read-only (by the caller), or
               at least should be treated as such.

               "optype" should be an opcode indicating the type of operation
               that the pad entry is to support.  This doesn't affect
               operational semantics, but is used for debugging.

                       PADOFFSET pad_alloc(I32 optype, U32 tmptype)

       pad_findmy_pv
               Exactly like "pad_findmy_pvn", but takes a nul-terminated
               string instead of a string/length pair.

                       PADOFFSET pad_findmy_pv(const char *name, U32 flags)

       pad_findmy_pvn
               Given the name of a lexical variable, find its position in the
               currently-compiling pad.  "namepv"/"namelen" specify the
               variable's name, including leading sigil.  "flags" is reserved
               and must be zero.  If it is not in the current pad but appears
               in the pad of any lexically enclosing scope, then a pseudo-
               entry for it is added in the current pad.  Returns the offset
               in the current pad, or "NOT_IN_PAD" if no such lexical is in
               scope.

                       PADOFFSET pad_findmy_pvn(const char *namepv,
                                                STRLEN namelen, U32 flags)

       pad_findmy_sv
               Exactly like "pad_findmy_pvn", but takes the name string in the
               form of an SV instead of a string/length pair.

                       PADOFFSET pad_findmy_sv(SV *name, U32 flags)

       padnamelist_fetch
               NOTE: this function is experimental and may change or be
               removed without notice.

               Fetches the pad name from the given index.

                       PADNAME * padnamelist_fetch(PADNAMELIST *pnl,
                                                   SSize_t key)

       padnamelist_store
               NOTE: this function is experimental and may change or be
               removed without notice.

               Stores the pad name (which may be null) at the given index,
               freeing any existing pad name in that slot.

                       PADNAME ** padnamelist_store(PADNAMELIST *pnl,
                                                    SSize_t key, PADNAME *val)

       pad_setsv
               Set the value at offset "po" in the current (compiling or
               executing) pad.  Use the macro "PAD_SETSV()" rather than
               calling this function directly.

                       void    pad_setsv(PADOFFSET po, SV *sv)

       pad_sv  Get the value at offset "po" in the current (compiling or
               executing) pad.  Use macro "PAD_SV" instead of calling this
               function directly.

                       SV *    pad_sv(PADOFFSET po)

       pad_tidy
               NOTE: this function is experimental and may change or be
               removed without notice.

               Tidy up a pad at the end of compilation of the code to which it
               belongs.  Jobs performed here are: remove most stuff from the
               pads of anonsub prototypes; give it a @_; mark temporaries as
               such.  "type" indicates the kind of subroutine:

                   padtidy_SUB        ordinary subroutine
                   padtidy_SUBCLONE   prototype for lexical closure
                   padtidy_FORMAT     format

                       void    pad_tidy(padtidy_type type)

       perl_alloc
               Allocates a new Perl interpreter.  See perlembed.

                       PerlInterpreter* perl_alloc()

       perl_construct
               Initializes a new Perl interpreter.  See perlembed.

                       void    perl_construct(PerlInterpreter *my_perl)

       perl_destruct
               Shuts down a Perl interpreter.  See perlembed for a tutorial.

               "my_perl" points to the Perl interpreter.  It must have been
               previously created through the use of "perl_alloc" and
               "perl_construct".  It may have been initialised through
               "perl_parse", and may have been used through "perl_run" and
               other means.  This function should be called for any Perl
               interpreter that has been constructed with "perl_construct",
               even if subsequent operations on it failed, for example if
               "perl_parse" returned a non-zero value.

               If the interpreter's "PL_exit_flags" word has the
               "PERL_EXIT_DESTRUCT_END" flag set, then this function will
               execute code in "END" blocks before performing the rest of
               destruction.  If it is desired to make any use of the
               interpreter between "perl_parse" and "perl_destruct" other than
               just calling "perl_run", then this flag should be set early on.
               This matters if "perl_run" will not be called, or if anything
               else will be done in addition to calling "perl_run".

               Returns a value be a suitable value to pass to the C library
               function "exit" (or to return from "main"), to serve as an exit
               code indicating the nature of the way the interpreter
               terminated.  This takes into account any failure of
               "perl_parse" and any early exit from "perl_run".  The exit code
               is of the type required by the host operating system, so
               because of differing exit code conventions it is not portable
               to interpret specific numeric values as having specific
               meanings.

                       int     perl_destruct(PerlInterpreter *my_perl)

       perl_free
               Releases a Perl interpreter.  See perlembed.

                       void    perl_free(PerlInterpreter *my_perl)

       perl_parse
               Tells a Perl interpreter to parse a Perl script.  This performs
               most of the initialisation of a Perl interpreter.  See
               perlembed for a tutorial.

               "my_perl" points to the Perl interpreter that is to parse the
               script.  It must have been previously created through the use
               of "perl_alloc" and "perl_construct".  "xsinit" points to a
               callback function that will be called to set up the ability for
               this Perl interpreter to load XS extensions, or may be null to
               perform no such setup.

               "argc" and "argv" supply a set of command-line arguments to the
               Perl interpreter, as would normally be passed to the "main"
               function of a C program.  "argv[argc]" must be null.  These
               arguments are where the script to parse is specified, either by
               naming a script file or by providing a script in a "-e" option.
               If $0 will be written to in the Perl interpreter, then the
               argument strings must be in writable memory, and so mustn't
               just be string constants.

               "env" specifies a set of environment variables that will be
               used by this Perl interpreter.  If non-null, it must point to a
               null-terminated array of environment strings.  If null, the
               Perl interpreter will use the environment supplied by the
               "environ" global variable.

               This function initialises the interpreter, and parses and
               compiles the script specified by the command-line arguments.
               This includes executing code in "BEGIN", "UNITCHECK", and
               "CHECK" blocks.  It does not execute "INIT" blocks or the main
               program.

               Returns an integer of slightly tricky interpretation.  The
               correct use of the return value is as a truth value indicating
               whether there was a failure in initialisation.  If zero is
               returned, this indicates that initialisation was successful,
               and it is safe to proceed to call "perl_run" and make other use
               of it.  If a non-zero value is returned, this indicates some
               problem that means the interpreter wants to terminate.  The
               interpreter should not be just abandoned upon such failure; the
               caller should proceed to shut the interpreter down cleanly with
               "perl_destruct" and free it with "perl_free".

               For historical reasons, the non-zero return value also attempts
               to be a suitable value to pass to the C library function "exit"
               (or to return from "main"), to serve as an exit code indicating
               the nature of the way initialisation terminated.  However, this
               isn't portable, due to differing exit code conventions.  A
               historical bug is preserved for the time being: if the Perl
               built-in "exit" is called during this function's execution,
               with a type of exit entailing a zero exit code under the host
               operating system's conventions, then this function returns zero
               rather than a non-zero value.  This bug, [perl #2754], leads to
               "perl_run" being called (and therefore "INIT" blocks and the
               main program running) despite a call to "exit".  It has been
               preserved because a popular module-installing module has come
               to rely on it and needs time to be fixed.  This issue is [perl
               #132577], and the original bug is due to be fixed in Perl 5.30.

                       int     perl_parse(PerlInterpreter *my_perl,
                                          XSINIT_t xsinit, int argc,
                                          char **argv, char **env)

       perl_run
               Tells a Perl interpreter to run its main program.  See
               perlembed for a tutorial.

               "my_perl" points to the Perl interpreter.  It must have been
               previously created through the use of "perl_alloc" and
               "perl_construct", and initialised through "perl_parse".  This
               function should not be called if "perl_parse" returned a non-
               zero value, indicating a failure in initialisation or
               compilation.

               This function executes code in "INIT" blocks, and then executes
               the main program.  The code to be executed is that established
               by the prior call to "perl_parse".  If the interpreter's
               "PL_exit_flags" word does not have the "PERL_EXIT_DESTRUCT_END"
               flag set, then this function will also execute code in "END"
               blocks.  If it is desired to make any further use of the
               interpreter after calling this function, then "END" blocks
               should be postponed to "perl_destruct" time by setting that
               flag.

               Returns an integer of slightly tricky interpretation.  The
               correct use of the return value is as a truth value indicating
               whether the program terminated non-locally.  If zero is
               returned, this indicates that the program ran to completion,
               and it is safe to make other use of the interpreter (provided
               that the "PERL_EXIT_DESTRUCT_END" flag was set as described
               above).  If a non-zero value is returned, this indicates that
               the interpreter wants to terminate early.  The interpreter
               should not be just abandoned because of this desire to
               terminate; the caller should proceed to shut the interpreter
               down cleanly with "perl_destruct" and free it with "perl_free".

               For historical reasons, the non-zero return value also attempts
               to be a suitable value to pass to the C library function "exit"
               (or to return from "main"), to serve as an exit code indicating
               the nature of the way the program terminated.  However, this
               isn't portable, due to differing exit code conventions.  An
               attempt is made to return an exit code of the type required by
               the host operating system, but because it is constrained to be
               non-zero, it is not necessarily possible to indicate every type
               of exit.  It is only reliable on Unix, where a zero exit code
               can be augmented with a set bit that will be ignored.  In any
               case, this function is not the correct place to acquire an exit
               code: one should get that from "perl_destruct".

                       int     perl_run(PerlInterpreter *my_perl)

       require_pv
               Tells Perl to "require" the file named by the string argument.
               It is analogous to the Perl code "eval "require '$file'"".
               It's even implemented that way; consider using load_module
               instead.

               NOTE: the perl_ form of this function is deprecated.

                       void    require_pv(const char* pv)

Exception Handling (simple) Macros
       dXCPT   Set up necessary local variables for exception handling.  See
               "Exception Handling" in perlguts.

                               dXCPT;

       XCPT_CATCH
               Introduces a catch block.  See "Exception Handling" in
               perlguts.

       XCPT_RETHROW
               Rethrows a previously caught exception.  See "Exception
               Handling" in perlguts.

                               XCPT_RETHROW;

       XCPT_TRY_END
               Ends a try block.  See "Exception Handling" in perlguts.

       XCPT_TRY_START
               Starts a try block.  See "Exception Handling" in perlguts.

Functions in file pp_sort.c
       sortsv_flags
               In-place sort an array of SV pointers with the given comparison
               routine, with various SORTf_* flag options.

                       void    sortsv_flags(SV** array, size_t num_elts,
                                            SVCOMPARE_t cmp, U32 flags)

Functions in file scope.c
       save_gp Saves the current GP of gv on the save stack to be restored on
               scope exit.

               If empty is true, replace the GP with a new GP.

               If empty is false, mark gv with GVf_INTRO so the next reference
               assigned is localized, which is how " local *foo = $someref; "
               works.

                       void    save_gp(GV* gv, I32 empty)

Functions in file vutil.c
       new_version
               Returns a new version object based on the passed in SV:

                   SV *sv = new_version(SV *ver);

               Does not alter the passed in ver SV.  See "upg_version" if you
               want to upgrade the SV.

                       SV*     new_version(SV *ver)

       prescan_version
               Validate that a given string can be parsed as a version object,
               but doesn't actually perform the parsing.  Can use either
               strict or lax validation rules.  Can optionally set a number of
               hint variables to save the parsing code some time when
               tokenizing.

                       const char* prescan_version(const char *s, bool strict,
                                                   const char** errstr,
                                                   bool *sqv,
                                                   int *ssaw_decimal,
                                                   int *swidth, bool *salpha)

       scan_version
               Returns a pointer to the next character after the parsed
               version string, as well as upgrading the passed in SV to an RV.

               Function must be called with an already existing SV like

                   sv = newSV(0);
                   s = scan_version(s, SV *sv, bool qv);

               Performs some preprocessing to the string to ensure that it has
               the correct characteristics of a version.  Flags the object if
               it contains an underscore (which denotes this is an alpha
               version).  The boolean qv denotes that the version should be
               interpreted as if it had multiple decimals, even if it doesn't.

                       const char* scan_version(const char *s, SV *rv, bool qv)

       upg_version
               In-place upgrade of the supplied SV to a version object.

                   SV *sv = upg_version(SV *sv, bool qv);

               Returns a pointer to the upgraded SV.  Set the boolean qv if
               you want to force this SV to be interpreted as an "extended"
               version.

                       SV*     upg_version(SV *ver, bool qv)

       vcmp    Version object aware cmp.  Both operands must already have been
               converted into version objects.

                       int     vcmp(SV *lhv, SV *rhv)

       vnormal Accepts a version object and returns the normalized string
               representation.  Call like:

                   sv = vnormal(rv);

               NOTE: you can pass either the object directly or the SV
               contained within the RV.

               The SV returned has a refcount of 1.

                       SV*     vnormal(SV *vs)

       vnumify Accepts a version object and returns the normalized floating
               point representation.  Call like:

                   sv = vnumify(rv);

               NOTE: you can pass either the object directly or the SV
               contained within the RV.

               The SV returned has a refcount of 1.

                       SV*     vnumify(SV *vs)

       vstringify
               In order to maintain maximum compatibility with earlier
               versions of Perl, this function will return either the floating
               point notation or the multiple dotted notation, depending on
               whether the original version contained 1 or more dots,
               respectively.

               The SV returned has a refcount of 1.

                       SV*     vstringify(SV *vs)

       vverify Validates that the SV contains valid internal structure for a
               version object.  It may be passed either the version object
               (RV) or the hash itself (HV).  If the structure is valid, it
               returns the HV.  If the structure is invalid, it returns NULL.

                   SV *hv = vverify(sv);

               Note that it only confirms the bare minimum structure (so as
               not to get confused by derived classes which may contain
               additional hash entries):

               o   The SV is an HV or a reference to an HV

               o   The hash contains a "version" key

               o   The "version" key has a reference to an AV as its value

                       SV*     vverify(SV *vs)

"Gimme" Values
       G_ARRAY Used to indicate list context.  See "GIMME_V", "GIMME" and
               perlcall.

       G_DISCARD
               Indicates that arguments returned from a callback should be
               discarded.  See perlcall.

       G_EVAL  Used to force a Perl "eval" wrapper around a callback.  See
               perlcall.

       GIMME   A backward-compatible version of "GIMME_V" which can only
               return "G_SCALAR" or "G_ARRAY"; in a void context, it returns
               "G_SCALAR".  Deprecated.  Use "GIMME_V" instead.

                       U32     GIMME

       GIMME_V The XSUB-writer's equivalent to Perl's "wantarray".  Returns
               "G_VOID", "G_SCALAR" or "G_ARRAY" for void, scalar or list
               context, respectively.  See perlcall for a usage example.

                       U32     GIMME_V

       G_NOARGS
               Indicates that no arguments are being sent to a callback.  See
               perlcall.

       G_SCALAR
               Used to indicate scalar context.  See "GIMME_V", "GIMME", and
               perlcall.

       G_VOID  Used to indicate void context.  See "GIMME_V" and perlcall.

Global Variables
       These variables are global to an entire process.  They are shared
       between all interpreters and all threads in a process.  Any variables
       not documented here may be changed or removed without notice, so don't
       use them!  If you feel you really do need to use an unlisted variable,
       first send email to perl5-porters@perl.org
       <mailto:perl5-porters@perl.org>.  It may be that someone there will
       point out a way to accomplish what you need without using an internal
       variable.  But if not, you should get a go-ahead to document and then
       use the variable.

       PL_check
               Array, indexed by opcode, of functions that will be called for
               the "check" phase of optree building during compilation of Perl
               code.  For most (but not all) types of op, once the op has been
               initially built and populated with child ops it will be
               filtered through the check function referenced by the
               appropriate element of this array.  The new op is passed in as
               the sole argument to the check function, and the check function
               returns the completed op.  The check function may (as the name
               suggests) check the op for validity and signal errors.  It may
               also initialise or modify parts of the ops, or perform more
               radical surgery such as adding or removing child ops, or even
               throw the op away and return a different op in its place.

               This array of function pointers is a convenient place to hook
               into the compilation process.  An XS module can put its own
               custom check function in place of any of the standard ones, to
               influence the compilation of a particular type of op.  However,
               a custom check function must never fully replace a standard
               check function (or even a custom check function from another
               module).  A module modifying checking must instead wrap the
               preexisting check function.  A custom check function must be
               selective about when to apply its custom behaviour.  In the
               usual case where it decides not to do anything special with an
               op, it must chain the preexisting op function.  Check functions
               are thus linked in a chain, with the core's base checker at the
               end.

               For thread safety, modules should not write directly to this
               array.  Instead, use the function "wrap_op_checker".

       PL_keyword_plugin
               NOTE: this function is experimental and may change or be
               removed without notice.

               Function pointer, pointing at a function used to handle
               extended keywords.  The function should be declared as

                       int keyword_plugin_function(pTHX_
                               char *keyword_ptr, STRLEN keyword_len,
                               OP **op_ptr)

               The function is called from the tokeniser, whenever a possible
               keyword is seen.  "keyword_ptr" points at the word in the
               parser's input buffer, and "keyword_len" gives its length; it
               is not null-terminated.  The function is expected to examine
               the word, and possibly other state such as %^H, to decide
               whether it wants to handle it as an extended keyword.  If it
               does not, the function should return "KEYWORD_PLUGIN_DECLINE",
               and the normal parser process will continue.

               If the function wants to handle the keyword, it first must
               parse anything following the keyword that is part of the syntax
               introduced by the keyword.  See "Lexer interface" for details.

               When a keyword is being handled, the plugin function must build
               a tree of "OP" structures, representing the code that was
               parsed.  The root of the tree must be stored in *op_ptr.  The
               function then returns a constant indicating the syntactic role
               of the construct that it has parsed: "KEYWORD_PLUGIN_STMT" if
               it is a complete statement, or "KEYWORD_PLUGIN_EXPR" if it is
               an expression.  Note that a statement construct cannot be used
               inside an expression (except via "do BLOCK" and similar), and
               an expression is not a complete statement (it requires at least
               a terminating semicolon).

               When a keyword is handled, the plugin function may also have
               (compile-time) side effects.  It may modify "%^H", define
               functions, and so on.  Typically, if side effects are the main
               purpose of a handler, it does not wish to generate any ops to
               be included in the normal compilation.  In this case it is
               still required to supply an op tree, but it suffices to
               generate a single null op.

               That's how the *PL_keyword_plugin function needs to behave
               overall.  Conventionally, however, one does not completely
               replace the existing handler function.  Instead, take a copy of
               "PL_keyword_plugin" before assigning your own function pointer
               to it.  Your handler function should look for keywords that it
               is interested in and handle those.  Where it is not interested,
               it should call the saved plugin function, passing on the
               arguments it received.  Thus "PL_keyword_plugin" actually
               points at a chain of handler functions, all of which have an
               opportunity to handle keywords, and only the last function in
               the chain (built into the Perl core) will normally return
               "KEYWORD_PLUGIN_DECLINE".

               For thread safety, modules should not set this variable
               directly.  Instead, use the function "wrap_keyword_plugin".

GV Functions
       A GV is a structure which corresponds to to a Perl typeglob, ie *foo.
       It is a structure that holds a pointer to a scalar, an array, a hash
       etc, corresponding to $foo, @foo, %foo.

       GVs are usually found as values in stashes (symbol table hashes) where
       Perl stores its global variables.

       GvAV    Return the AV from the GV.

                       AV*     GvAV(GV* gv)

       gv_const_sv
               If "gv" is a typeglob whose subroutine entry is a constant sub
               eligible for inlining, or "gv" is a placeholder reference that
               would be promoted to such a typeglob, then returns the value
               returned by the sub.  Otherwise, returns "NULL".

                       SV*     gv_const_sv(GV* gv)

       GvCV    Return the CV from the GV.

                       CV*     GvCV(GV* gv)

       gv_fetchmeth
               Like "gv_fetchmeth_pvn", but lacks a flags parameter.

                       GV*     gv_fetchmeth(HV* stash, const char* name,
                                            STRLEN len, I32 level)

       gv_fetchmethod_autoload
               Returns the glob which contains the subroutine to call to
               invoke the method on the "stash".  In fact in the presence of
               autoloading this may be the glob for "AUTOLOAD".  In this case
               the corresponding variable $AUTOLOAD is already setup.

               The third parameter of "gv_fetchmethod_autoload" determines
               whether AUTOLOAD lookup is performed if the given method is not
               present: non-zero means yes, look for AUTOLOAD; zero means no,
               don't look for AUTOLOAD.  Calling "gv_fetchmethod" is
               equivalent to calling "gv_fetchmethod_autoload" with a non-zero
               "autoload" parameter.

               These functions grant "SUPER" token as a prefix of the method
               name.  Note that if you want to keep the returned glob for a
               long time, you need to check for it being "AUTOLOAD", since at
               the later time the call may load a different subroutine due to
               $AUTOLOAD changing its value.  Use the glob created as a side
               effect to do this.

               These functions have the same side-effects as "gv_fetchmeth"
               with "level==0".  The warning against passing the GV returned
               by "gv_fetchmeth" to "call_sv" applies equally to these
               functions.

                       GV*     gv_fetchmethod_autoload(HV* stash,
                                                       const char* name,
                                                       I32 autoload)

       gv_fetchmeth_autoload
               This is the old form of "gv_fetchmeth_pvn_autoload", which has
               no flags parameter.

                       GV*     gv_fetchmeth_autoload(HV* stash,
                                                     const char* name,
                                                     STRLEN len, I32 level)

       gv_fetchmeth_pv
               Exactly like "gv_fetchmeth_pvn", but takes a nul-terminated
               string instead of a string/length pair.

                       GV*     gv_fetchmeth_pv(HV* stash, const char* name,
                                               I32 level, U32 flags)

       gv_fetchmeth_pvn
               Returns the glob with the given "name" and a defined subroutine
               or "NULL".  The glob lives in the given "stash", or in the
               stashes accessible via @ISA and "UNIVERSAL::".

               The argument "level" should be either 0 or -1.  If "level==0",
               as a side-effect creates a glob with the given "name" in the
               given "stash" which in the case of success contains an alias
               for the subroutine, and sets up caching info for this glob.

               The only significant values for "flags" are "GV_SUPER" and
               "SVf_UTF8".

               "GV_SUPER" indicates that we want to look up the method in the
               superclasses of the "stash".

               The GV returned from "gv_fetchmeth" may be a method cache
               entry, which is not visible to Perl code.  So when calling
               "call_sv", you should not use the GV directly; instead, you
               should use the method's CV, which can be obtained from the GV
               with the "GvCV" macro.

                       GV*     gv_fetchmeth_pvn(HV* stash, const char* name,
                                                STRLEN len, I32 level,
                                                U32 flags)

       gv_fetchmeth_pvn_autoload
               Same as "gv_fetchmeth_pvn()", but looks for autoloaded
               subroutines too.  Returns a glob for the subroutine.

               For an autoloaded subroutine without a GV, will create a GV
               even if "level < 0".  For an autoloaded subroutine without a
               stub, "GvCV()" of the result may be zero.

               Currently, the only significant value for "flags" is
               "SVf_UTF8".

                       GV*     gv_fetchmeth_pvn_autoload(HV* stash,
                                                         const char* name,
                                                         STRLEN len, I32 level,
                                                         U32 flags)

       gv_fetchmeth_pv_autoload
               Exactly like "gv_fetchmeth_pvn_autoload", but takes a nul-
               terminated string instead of a string/length pair.

                       GV*     gv_fetchmeth_pv_autoload(HV* stash,
                                                        const char* name,
                                                        I32 level, U32 flags)

       gv_fetchmeth_sv
               Exactly like "gv_fetchmeth_pvn", but takes the name string in
               the form of an SV instead of a string/length pair.

                       GV*     gv_fetchmeth_sv(HV* stash, SV* namesv,
                                               I32 level, U32 flags)

       gv_fetchmeth_sv_autoload
               Exactly like "gv_fetchmeth_pvn_autoload", but takes the name
               string in the form of an SV instead of a string/length pair.

                       GV*     gv_fetchmeth_sv_autoload(HV* stash, SV* namesv,
                                                        I32 level, U32 flags)

       GvHV    Return the HV from the GV.

                       HV*     GvHV(GV* gv)

       gv_init The old form of "gv_init_pvn()".  It does not work with UTF-8
               strings, as it has no flags parameter.  If the "multi"
               parameter is set, the "GV_ADDMULTI" flag will be passed to
               "gv_init_pvn()".

                       void    gv_init(GV* gv, HV* stash, const char* name,
                                       STRLEN len, int multi)

       gv_init_pv
               Same as "gv_init_pvn()", but takes a nul-terminated string for
               the name instead of separate char * and length parameters.

                       void    gv_init_pv(GV* gv, HV* stash, const char* name,
                                          U32 flags)

       gv_init_pvn
               Converts a scalar into a typeglob.  This is an incoercible
               typeglob; assigning a reference to it will assign to one of its
               slots, instead of overwriting it as happens with typeglobs
               created by "SvSetSV".  Converting any scalar that is "SvOK()"
               may produce unpredictable results and is reserved for perl's
               internal use.

               "gv" is the scalar to be converted.

               "stash" is the parent stash/package, if any.

               "name" and "len" give the name.  The name must be unqualified;
               that is, it must not include the package name.  If "gv" is a
               stash element, it is the caller's responsibility to ensure that
               the name passed to this function matches the name of the
               element.  If it does not match, perl's internal bookkeeping
               will get out of sync.

               "flags" can be set to "SVf_UTF8" if "name" is a UTF-8 string,
               or the return value of SvUTF8(sv).  It can also take the
               "GV_ADDMULTI" flag, which means to pretend that the GV has been
               seen before (i.e., suppress "Used once" warnings).

                       void    gv_init_pvn(GV* gv, HV* stash, const char* name,
                                           STRLEN len, U32 flags)

       gv_init_sv
               Same as "gv_init_pvn()", but takes an SV * for the name instead
               of separate char * and length parameters.  "flags" is currently
               unused.

                       void    gv_init_sv(GV* gv, HV* stash, SV* namesv,
                                          U32 flags)

       gv_stashpv
               Returns a pointer to the stash for a specified package.  Uses
               "strlen" to determine the length of "name", then calls
               "gv_stashpvn()".

                       HV*     gv_stashpv(const char* name, I32 flags)

       gv_stashpvn
               Returns a pointer to the stash for a specified package.  The
               "namelen" parameter indicates the length of the "name", in
               bytes.  "flags" is passed to "gv_fetchpvn_flags()", so if set
               to "GV_ADD" then the package will be created if it does not
               already exist.  If the package does not exist and "flags" is 0
               (or any other setting that does not create packages) then
               "NULL" is returned.

               Flags may be one of:

                   GV_ADD
                   SVf_UTF8
                   GV_NOADD_NOINIT
                   GV_NOINIT
                   GV_NOEXPAND
                   GV_ADDMG

               The most important of which are probably "GV_ADD" and
               "SVf_UTF8".

               Note, use of "gv_stashsv" instead of "gv_stashpvn" where
               possible is strongly recommended for performance reasons.

                       HV*     gv_stashpvn(const char* name, U32 namelen,
                                           I32 flags)

       gv_stashpvs
               Like "gv_stashpvn", but takes a literal string instead of a
               string/length pair.

                       HV*     gv_stashpvs("literal string" name, I32 create)

       gv_stashsv
               Returns a pointer to the stash for a specified package.  See
               "gv_stashpvn".

               Note this interface is strongly preferred over "gv_stashpvn"
               for performance reasons.

                       HV*     gv_stashsv(SV* sv, I32 flags)

       GvSV    Return the SV from the GV.

                       SV*     GvSV(GV* gv)

       setdefout
               Sets "PL_defoutgv", the default file handle for output, to the
               passed in typeglob.  As "PL_defoutgv" "owns" a reference on its
               typeglob, the reference count of the passed in typeglob is
               increased by one, and the reference count of the typeglob that
               "PL_defoutgv" points to is decreased by one.

                       void    setdefout(GV* gv)

Handy Values
       Nullav  Null AV pointer.

               (deprecated - use "(AV *)NULL" instead)

       Nullch  Null character pointer.  (No longer available when "PERL_CORE"
               is defined.)

       Nullcv  Null CV pointer.

               (deprecated - use "(CV *)NULL" instead)

       Nullhv  Null HV pointer.

               (deprecated - use "(HV *)NULL" instead)

       Nullsv  Null SV pointer.  (No longer available when "PERL_CORE" is
               defined.)

Hash Manipulation Functions
       A HV structure represents a Perl hash.  It consists mainly of an array
       of pointers, each of which points to a linked list of HE structures.
       The array is indexed by the hash function of the key, so each linked
       list represents all the hash entries with the same hash value.  Each HE
       contains a pointer to the actual value, plus a pointer to a HEK
       structure which holds the key and hash value.

       cop_fetch_label
               NOTE: this function is experimental and may change or be
               removed without notice.

               Returns the label attached to a cop.  The flags pointer may be
               set to "SVf_UTF8" or 0.

                       const char * cop_fetch_label(COP *const cop,
                                                    STRLEN *len, U32 *flags)

       cop_store_label
               NOTE: this function is experimental and may change or be
               removed without notice.

               Save a label into a "cop_hints_hash".  You need to set flags to
               "SVf_UTF8" for a UTF-8 label.

                       void    cop_store_label(COP *const cop,
                                               const char *label, STRLEN len,
                                               U32 flags)

       get_hv  Returns the HV of the specified Perl hash.  "flags" are passed
               to "gv_fetchpv".  If "GV_ADD" is set and the Perl variable does
               not exist then it will be created.  If "flags" is zero and the
               variable does not exist then "NULL" is returned.

               NOTE: the perl_ form of this function is deprecated.

                       HV*     get_hv(const char *name, I32 flags)

       HEf_SVKEY
               This flag, used in the length slot of hash entries and magic
               structures, specifies the structure contains an "SV*" pointer
               where a "char*" pointer is to be expected.  (For information
               only--not to be used).

       HeHASH  Returns the computed hash stored in the hash entry.

                       U32     HeHASH(HE* he)

       HeKEY   Returns the actual pointer stored in the key slot of the hash
               entry.  The pointer may be either "char*" or "SV*", depending
               on the value of "HeKLEN()".  Can be assigned to.  The "HePV()"
               or "HeSVKEY()" macros are usually preferable for finding the
               value of a key.

                       void*   HeKEY(HE* he)

       HeKLEN  If this is negative, and amounts to "HEf_SVKEY", it indicates
               the entry holds an "SV*" key.  Otherwise, holds the actual
               length of the key.  Can be assigned to.  The "HePV()" macro is
               usually preferable for finding key lengths.

                       STRLEN  HeKLEN(HE* he)

       HePV    Returns the key slot of the hash entry as a "char*" value,
               doing any necessary dereferencing of possibly "SV*" keys.  The
               length of the string is placed in "len" (this is a macro, so do
               not use &len).  If you do not care about what the length of the
               key is, you may use the global variable "PL_na", though this is
               rather less efficient than using a local variable.  Remember
               though, that hash keys in perl are free to contain embedded
               nulls, so using "strlen()" or similar is not a good way to find
               the length of hash keys.  This is very similar to the "SvPV()"
               macro described elsewhere in this document.  See also "HeUTF8".

               If you are using "HePV" to get values to pass to "newSVpvn()"
               to create a new SV, you should consider using
               "newSVhek(HeKEY_hek(he))" as it is more efficient.

                       char*   HePV(HE* he, STRLEN len)

       HeSVKEY Returns the key as an "SV*", or "NULL" if the hash entry does
               not contain an "SV*" key.

                       SV*     HeSVKEY(HE* he)

       HeSVKEY_force
               Returns the key as an "SV*".  Will create and return a
               temporary mortal "SV*" if the hash entry contains only a
               "char*" key.

                       SV*     HeSVKEY_force(HE* he)

       HeSVKEY_set
               Sets the key to a given "SV*", taking care to set the
               appropriate flags to indicate the presence of an "SV*" key, and
               returns the same "SV*".

                       SV*     HeSVKEY_set(HE* he, SV* sv)

       HeUTF8  Returns whether the "char *" value returned by "HePV" is
               encoded in UTF-8, doing any necessary dereferencing of possibly
               "SV*" keys.  The value returned will be 0 or non-0, not
               necessarily 1 (or even a value with any low bits set), so do
               not blindly assign this to a "bool" variable, as "bool" may be
               a typedef for "char".

                       U32     HeUTF8(HE* he)

       HeVAL   Returns the value slot (type "SV*") stored in the hash entry.
               Can be assigned to.

                 SV *foo= HeVAL(hv);
                 HeVAL(hv)= sv;

                       SV*     HeVAL(HE* he)

       hv_assert
               Check that a hash is in an internally consistent state.

                       void    hv_assert(HV *hv)

       hv_bucket_ratio
               NOTE: this function is experimental and may change or be
               removed without notice.

               If the hash is tied dispatches through to the SCALAR tied
               method, otherwise if the hash contains no keys returns 0,
               otherwise returns a mortal sv containing a string specifying
               the number of used buckets, followed by a slash, followed by
               the number of available buckets.

               This function is expensive, it must scan all of the buckets to
               determine which are used, and the count is NOT cached.  In a
               large hash this could be a lot of buckets.

                       SV*     hv_bucket_ratio(HV *hv)

       hv_clear
               Frees the all the elements of a hash, leaving it empty.  The XS
               equivalent of "%hash = ()".  See also "hv_undef".

               See "av_clear" for a note about the hash possibly being invalid
               on return.

                       void    hv_clear(HV *hv)

       hv_clear_placeholders
               Clears any placeholders from a hash.  If a restricted hash has
               any of its keys marked as readonly and the key is subsequently
               deleted, the key is not actually deleted but is marked by
               assigning it a value of &PL_sv_placeholder.  This tags it so it
               will be ignored by future operations such as iterating over the
               hash, but will still allow the hash to have a value reassigned
               to the key at some future point.  This function clears any such
               placeholder keys from the hash.  See "Hash::Util::lock_keys()"
               for an example of its use.

                       void    hv_clear_placeholders(HV *hv)

       hv_copy_hints_hv
               A specialised version of "newHVhv" for copying "%^H".  "ohv"
               must be a pointer to a hash (which may have "%^H" magic, but
               should be generally non-magical), or "NULL" (interpreted as an
               empty hash).  The content of "ohv" is copied to a new hash,
               which has the "%^H"-specific magic added to it.  A pointer to
               the new hash is returned.

                       HV *    hv_copy_hints_hv(HV *ohv)

       hv_delete
               Deletes a key/value pair in the hash.  The value's SV is
               removed from the hash, made mortal, and returned to the caller.
               The absolute value of "klen" is the length of the key.  If
               "klen" is negative the key is assumed to be in UTF-8-encoded
               Unicode.  The "flags" value will normally be zero; if set to
               "G_DISCARD" then "NULL" will be returned.  "NULL" will also be
               returned if the key is not found.

                       SV*     hv_delete(HV *hv, const char *key, I32 klen,
                                         I32 flags)

       hv_delete_ent
               Deletes a key/value pair in the hash.  The value SV is removed
               from the hash, made mortal, and returned to the caller.  The
               "flags" value will normally be zero; if set to "G_DISCARD" then
               "NULL" will be returned.  "NULL" will also be returned if the
               key is not found.  "hash" can be a valid precomputed hash
               value, or 0 to ask for it to be computed.

                       SV*     hv_delete_ent(HV *hv, SV *keysv, I32 flags,
                                             U32 hash)

       HvENAME Returns the effective name of a stash, or NULL if there is
               none.  The effective name represents a location in the symbol
               table where this stash resides.  It is updated automatically
               when packages are aliased or deleted.  A stash that is no
               longer in the symbol table has no effective name.  This name is
               preferable to "HvNAME" for use in MRO linearisations and isa
               caches.

                       char*   HvENAME(HV* stash)

       HvENAMELEN
               Returns the length of the stash's effective name.

                       STRLEN  HvENAMELEN(HV *stash)

       HvENAMEUTF8
               Returns true if the effective name is in UTF-8 encoding.

                       unsigned char HvENAMEUTF8(HV *stash)

       hv_exists
               Returns a boolean indicating whether the specified hash key
               exists.  The absolute value of "klen" is the length of the key.
               If "klen" is negative the key is assumed to be in UTF-8-encoded
               Unicode.

                       bool    hv_exists(HV *hv, const char *key, I32 klen)

       hv_exists_ent
               Returns a boolean indicating whether the specified hash key
               exists.  "hash" can be a valid precomputed hash value, or 0 to
               ask for it to be computed.

                       bool    hv_exists_ent(HV *hv, SV *keysv, U32 hash)

       hv_fetch
               Returns the SV which corresponds to the specified key in the
               hash.  The absolute value of "klen" is the length of the key.
               If "klen" is negative the key is assumed to be in UTF-8-encoded
               Unicode.  If "lval" is set then the fetch will be part of a
               store.  This means that if there is no value in the hash
               associated with the given key, then one is created and a
               pointer to it is returned.  The "SV*" it points to can be
               assigned to.  But always check that the return value is non-
               null before dereferencing it to an "SV*".

               See "Understanding the Magic of Tied Hashes and Arrays" in
               perlguts for more information on how to use this function on
               tied hashes.

                       SV**    hv_fetch(HV *hv, const char *key, I32 klen,
                                        I32 lval)

       hv_fetchs
               Like "hv_fetch", but takes a literal string instead of a
               string/length pair.

                       SV**    hv_fetchs(HV* tb, "literal string" key,
                                         I32 lval)

       hv_fetch_ent
               Returns the hash entry which corresponds to the specified key
               in the hash.  "hash" must be a valid precomputed hash number
               for the given "key", or 0 if you want the function to compute
               it.  IF "lval" is set then the fetch will be part of a store.
               Make sure the return value is non-null before accessing it.
               The return value when "hv" is a tied hash is a pointer to a
               static location, so be sure to make a copy of the structure if
               you need to store it somewhere.

               See "Understanding the Magic of Tied Hashes and Arrays" in
               perlguts for more information on how to use this function on
               tied hashes.

                       HE*     hv_fetch_ent(HV *hv, SV *keysv, I32 lval,
                                            U32 hash)

       hv_fill Returns the number of hash buckets that happen to be in use.

               This function is wrapped by the macro "HvFILL".

               As of perl 5.25 this function is used only for debugging
               purposes, and the number of used hash buckets is not in any way
               cached, thus this function can be costly to execute as it must
               iterate over all the buckets in the hash.

                       STRLEN  hv_fill(HV *const hv)

       hv_iterinit
               Prepares a starting point to traverse a hash table.  Returns
               the number of keys in the hash, including placeholders (i.e.
               the same as "HvTOTALKEYS(hv)").  The return value is currently
               only meaningful for hashes without tie magic.

               NOTE: Before version 5.004_65, "hv_iterinit" used to return the
               number of hash buckets that happen to be in use.  If you still
               need that esoteric value, you can get it through the macro
               "HvFILL(hv)".

                       I32     hv_iterinit(HV *hv)

       hv_iterkey
               Returns the key from the current position of the hash iterator.
               See "hv_iterinit".

                       char*   hv_iterkey(HE* entry, I32* retlen)

       hv_iterkeysv
               Returns the key as an "SV*" from the current position of the
               hash iterator.  The return value will always be a mortal copy
               of the key.  Also see "hv_iterinit".

                       SV*     hv_iterkeysv(HE* entry)

       hv_iternext
               Returns entries from a hash iterator.  See "hv_iterinit".

               You may call "hv_delete" or "hv_delete_ent" on the hash entry
               that the iterator currently points to, without losing your
               place or invalidating your iterator.  Note that in this case
               the current entry is deleted from the hash with your iterator
               holding the last reference to it.  Your iterator is flagged to
               free the entry on the next call to "hv_iternext", so you must
               not discard your iterator immediately else the entry will leak
               - call "hv_iternext" to trigger the resource deallocation.

                       HE*     hv_iternext(HV *hv)

       hv_iternextsv
               Performs an "hv_iternext", "hv_iterkey", and "hv_iterval" in
               one operation.

                       SV*     hv_iternextsv(HV *hv, char **key, I32 *retlen)

       hv_iternext_flags
               NOTE: this function is experimental and may change or be
               removed without notice.

               Returns entries from a hash iterator.  See "hv_iterinit" and
               "hv_iternext".  The "flags" value will normally be zero; if
               "HV_ITERNEXT_WANTPLACEHOLDERS" is set the placeholders keys
               (for restricted hashes) will be returned in addition to normal
               keys.  By default placeholders are automatically skipped over.
               Currently a placeholder is implemented with a value that is
               &PL_sv_placeholder.  Note that the implementation of
               placeholders and restricted hashes may change, and the
               implementation currently is insufficiently abstracted for any
               change to be tidy.

                       HE*     hv_iternext_flags(HV *hv, I32 flags)

       hv_iterval
               Returns the value from the current position of the hash
               iterator.  See "hv_iterkey".

                       SV*     hv_iterval(HV *hv, HE *entry)

       hv_magic
               Adds magic to a hash.  See "sv_magic".

                       void    hv_magic(HV *hv, GV *gv, int how)

       HvNAME  Returns the package name of a stash, or "NULL" if "stash" isn't
               a stash.  See "SvSTASH", "CvSTASH".

                       char*   HvNAME(HV* stash)

       HvNAMELEN
               Returns the length of the stash's name.

                       STRLEN  HvNAMELEN(HV *stash)

       HvNAMEUTF8
               Returns true if the name is in UTF-8 encoding.

                       unsigned char HvNAMEUTF8(HV *stash)

       hv_scalar
               Evaluates the hash in scalar context and returns the result.

               When the hash is tied dispatches through to the SCALAR method,
               otherwise returns a mortal SV containing the number of keys in
               the hash.

               Note, prior to 5.25 this function returned what is now returned
               by the hv_bucket_ratio() function.

                       SV*     hv_scalar(HV *hv)

       hv_store
               Stores an SV in a hash.  The hash key is specified as "key" and
               the absolute value of "klen" is the length of the key.  If
               "klen" is negative the key is assumed to be in UTF-8-encoded
               Unicode.  The "hash" parameter is the precomputed hash value;
               if it is zero then Perl will compute it.

               The return value will be "NULL" if the operation failed or if
               the value did not need to be actually stored within the hash
               (as in the case of tied hashes).  Otherwise it can be
               dereferenced to get the original "SV*".  Note that the caller
               is responsible for suitably incrementing the reference count of
               "val" before the call, and decrementing it if the function
               returned "NULL".  Effectively a successful "hv_store" takes
               ownership of one reference to "val".  This is usually what you
               want; a newly created SV has a reference count of one, so if
               all your code does is create SVs then store them in a hash,
               "hv_store" will own the only reference to the new SV, and your
               code doesn't need to do anything further to tidy up.
               "hv_store" is not implemented as a call to "hv_store_ent", and
               does not create a temporary SV for the key, so if your key data
               is not already in SV form then use "hv_store" in preference to
               "hv_store_ent".

               See "Understanding the Magic of Tied Hashes and Arrays" in
               perlguts for more information on how to use this function on
               tied hashes.

                       SV**    hv_store(HV *hv, const char *key, I32 klen,
                                        SV *val, U32 hash)

       hv_stores
               Like "hv_store", but takes a literal string instead of a
               string/length pair and omits the hash parameter.

                       SV**    hv_stores(HV* tb, "literal string" key, SV* val)

       hv_store_ent
               Stores "val" in a hash.  The hash key is specified as "key".
               The "hash" parameter is the precomputed hash value; if it is
               zero then Perl will compute it.  The return value is the new
               hash entry so created.  It will be "NULL" if the operation
               failed or if the value did not need to be actually stored
               within the hash (as in the case of tied hashes).  Otherwise the
               contents of the return value can be accessed using the "He?"
               macros described here.  Note that the caller is responsible for
               suitably incrementing the reference count of "val" before the
               call, and decrementing it if the function returned NULL.
               Effectively a successful "hv_store_ent" takes ownership of one
               reference to "val".  This is usually what you want; a newly
               created SV has a reference count of one, so if all your code
               does is create SVs then store them in a hash, "hv_store" will
               own the only reference to the new SV, and your code doesn't
               need to do anything further to tidy up.  Note that
               "hv_store_ent" only reads the "key"; unlike "val" it does not
               take ownership of it, so maintaining the correct reference
               count on "key" is entirely the caller's responsibility.  The
               reason it does not take ownership, is that "key" is not used
               after this function returns, and so can be freed immediately.
               "hv_store" is not implemented as a call to "hv_store_ent", and
               does not create a temporary SV for the key, so if your key data
               is not already in SV form then use "hv_store" in preference to
               "hv_store_ent".

               See "Understanding the Magic of Tied Hashes and Arrays" in
               perlguts for more information on how to use this function on
               tied hashes.

                       HE*     hv_store_ent(HV *hv, SV *key, SV *val, U32 hash)

       hv_undef
               Undefines the hash.  The XS equivalent of "undef(%hash)".

               As well as freeing all the elements of the hash (like
               "hv_clear()"), this also frees any auxiliary data and storage
               associated with the hash.

               See "av_clear" for a note about the hash possibly being invalid
               on return.

                       void    hv_undef(HV *hv)

       newHV   Creates a new HV.  The reference count is set to 1.

                       HV*     newHV()

Hook manipulation
       These functions provide convenient and thread-safe means of
       manipulating hook variables.

       wrap_op_checker
               Puts a C function into the chain of check functions for a
               specified op type.  This is the preferred way to manipulate the
               "PL_check" array.  "opcode" specifies which type of op is to be
               affected.  "new_checker" is a pointer to the C function that is
               to be added to that opcode's check chain, and "old_checker_p"
               points to the storage location where a pointer to the next
               function in the chain will be stored.  The value of
               "new_checker" is written into the "PL_check" array, while the
               value previously stored there is written to *old_checker_p.

               "PL_check" is global to an entire process, and a module wishing
               to hook op checking may find itself invoked more than once per
               process, typically in different threads.  To handle that
               situation, this function is idempotent.  The location
               *old_checker_p must initially (once per process) contain a null
               pointer.  A C variable of static duration (declared at file
               scope, typically also marked "static" to give it internal
               linkage) will be implicitly initialised appropriately, if it
               does not have an explicit initialiser.  This function will only
               actually modify the check chain if it finds *old_checker_p to
               be null.  This function is also thread safe on the small scale.
               It uses appropriate locking to avoid race conditions in
               accessing "PL_check".

               When this function is called, the function referenced by
               "new_checker" must be ready to be called, except for
               *old_checker_p being unfilled.  In a threading situation,
               "new_checker" may be called immediately, even before this
               function has returned.  *old_checker_p will always be
               appropriately set before "new_checker" is called.  If
               "new_checker" decides not to do anything special with an op
               that it is given (which is the usual case for most uses of op
               check hooking), it must chain the check function referenced by
               *old_checker_p.

               Taken all together, XS code to hook an op checker should
               typically look something like this:

                   static Perl_check_t nxck_frob;
                   static OP *myck_frob(pTHX_ OP *op) {
                       ...
                       op = nxck_frob(aTHX_ op);
                       ...
                       return op;
                   }
                   BOOT:
                       wrap_op_checker(OP_FROB, myck_frob, &nxck_frob);

               If you want to influence compilation of calls to a specific
               subroutine, then use "cv_set_call_checker_flags" rather than
               hooking checking of all "entersub" ops.

                       void    wrap_op_checker(Optype opcode,
                                               Perl_check_t new_checker,
                                               Perl_check_t *old_checker_p)

Lexer interface
       This is the lower layer of the Perl parser, managing characters and
       tokens.

       lex_bufutf8
               NOTE: this function is experimental and may change or be
               removed without notice.

               Indicates whether the octets in the lexer buffer
               ("PL_parser->linestr") should be interpreted as the UTF-8
               encoding of Unicode characters.  If not, they should be
               interpreted as Latin-1 characters.  This is analogous to the
               "SvUTF8" flag for scalars.

               In UTF-8 mode, it is not guaranteed that the lexer buffer
               actually contains valid UTF-8.  Lexing code must be robust in
               the face of invalid encoding.

               The actual "SvUTF8" flag of the "PL_parser->linestr" scalar is
               significant, but not the whole story regarding the input
               character encoding.  Normally, when a file is being read, the
               scalar contains octets and its "SvUTF8" flag is off, but the
               octets should be interpreted as UTF-8 if the "use utf8" pragma
               is in effect.  During a string eval, however, the scalar may
               have the "SvUTF8" flag on, and in this case its octets should
               be interpreted as UTF-8 unless the "use bytes" pragma is in
               effect.  This logic may change in the future; use this function
               instead of implementing the logic yourself.

                       bool    lex_bufutf8()

       lex_discard_to
               NOTE: this function is experimental and may change or be
               removed without notice.

               Discards the first part of the "PL_parser->linestr" buffer, up
               to "ptr".  The remaining content of the buffer will be moved,
               and all pointers into the buffer updated appropriately.  "ptr"
               must not be later in the buffer than the position of
               "PL_parser->bufptr": it is not permitted to discard text that
               has yet to be lexed.

               Normally it is not necessarily to do this directly, because it
               suffices to use the implicit discarding behaviour of
               "lex_next_chunk" and things based on it.  However, if a token
               stretches across multiple lines, and the lexing code has kept
               multiple lines of text in the buffer for that purpose, then
               after completion of the token it would be wise to explicitly
               discard the now-unneeded earlier lines, to avoid future multi-
               line tokens growing the buffer without bound.

                       void    lex_discard_to(char *ptr)

       lex_grow_linestr
               NOTE: this function is experimental and may change or be
               removed without notice.

               Reallocates the lexer buffer ("PL_parser->linestr") to
               accommodate at least "len" octets (including terminating
               "NUL").  Returns a pointer to the reallocated buffer.  This is
               necessary before making any direct modification of the buffer
               that would increase its length.  "lex_stuff_pvn" provides a
               more convenient way to insert text into the buffer.

               Do not use "SvGROW" or "sv_grow" directly on
               "PL_parser->linestr"; this function updates all of the lexer's
               variables that point directly into the buffer.

                       char *  lex_grow_linestr(STRLEN len)

       lex_next_chunk
               NOTE: this function is experimental and may change or be
               removed without notice.

               Reads in the next chunk of text to be lexed, appending it to
               "PL_parser->linestr".  This should be called when lexing code
               has looked to the end of the current chunk and wants to know
               more.  It is usual, but not necessary, for lexing to have
               consumed the entirety of the current chunk at this time.

               If "PL_parser->bufptr" is pointing to the very end of the
               current chunk (i.e., the current chunk has been entirely
               consumed), normally the current chunk will be discarded at the
               same time that the new chunk is read in.  If "flags" has the
               "LEX_KEEP_PREVIOUS" bit set, the current chunk will not be
               discarded.  If the current chunk has not been entirely
               consumed, then it will not be discarded regardless of the flag.

               Returns true if some new text was added to the buffer, or false
               if the buffer has reached the end of the input text.

                       bool    lex_next_chunk(U32 flags)

       lex_peek_unichar
               NOTE: this function is experimental and may change or be
               removed without notice.

               Looks ahead one (Unicode) character in the text currently being
               lexed.  Returns the codepoint (unsigned integer value) of the
               next character, or -1 if lexing has reached the end of the
               input text.  To consume the peeked character, use
               "lex_read_unichar".

               If the next character is in (or extends into) the next chunk of
               input text, the next chunk will be read in.  Normally the
               current chunk will be discarded at the same time, but if
               "flags" has the "LEX_KEEP_PREVIOUS" bit set, then the current
               chunk will not be discarded.

               If the input is being interpreted as UTF-8 and a UTF-8 encoding
               error is encountered, an exception is generated.

                       I32     lex_peek_unichar(U32 flags)

       lex_read_space
               NOTE: this function is experimental and may change or be
               removed without notice.

               Reads optional spaces, in Perl style, in the text currently
               being lexed.  The spaces may include ordinary whitespace
               characters and Perl-style comments.  "#line" directives are
               processed if encountered.  "PL_parser->bufptr" is moved past
               the spaces, so that it points at a non-space character (or the
               end of the input text).

               If spaces extend into the next chunk of input text, the next
               chunk will be read in.  Normally the current chunk will be
               discarded at the same time, but if "flags" has the
               "LEX_KEEP_PREVIOUS" bit set, then the current chunk will not be
               discarded.

                       void    lex_read_space(U32 flags)

       lex_read_to
               NOTE: this function is experimental and may change or be
               removed without notice.

               Consume text in the lexer buffer, from "PL_parser->bufptr" up
               to "ptr".  This advances "PL_parser->bufptr" to match "ptr",
               performing the correct bookkeeping whenever a newline character
               is passed.  This is the normal way to consume lexed text.

               Interpretation of the buffer's octets can be abstracted out by
               using the slightly higher-level functions "lex_peek_unichar"
               and "lex_read_unichar".

                       void    lex_read_to(char *ptr)

       lex_read_unichar
               NOTE: this function is experimental and may change or be
               removed without notice.

               Reads the next (Unicode) character in the text currently being
               lexed.  Returns the codepoint (unsigned integer value) of the
               character read, and moves "PL_parser->bufptr" past the
               character, or returns -1 if lexing has reached the end of the
               input text.  To non-destructively examine the next character,
               use "lex_peek_unichar" instead.

               If the next character is in (or extends into) the next chunk of
               input text, the next chunk will be read in.  Normally the
               current chunk will be discarded at the same time, but if
               "flags" has the "LEX_KEEP_PREVIOUS" bit set, then the current
               chunk will not be discarded.

               If the input is being interpreted as UTF-8 and a UTF-8 encoding
               error is encountered, an exception is generated.

                       I32     lex_read_unichar(U32 flags)

       lex_start
               NOTE: this function is experimental and may change or be
               removed without notice.

               Creates and initialises a new lexer/parser state object,
               supplying a context in which to lex and parse from a new source
               of Perl code.  A pointer to the new state object is placed in
               "PL_parser".  An entry is made on the save stack so that upon
               unwinding, the new state object will be destroyed and the
               former value of "PL_parser" will be restored.  Nothing else
               need be done to clean up the parsing context.

               The code to be parsed comes from "line" and "rsfp".  "line", if
               non-null, provides a string (in SV form) containing code to be
               parsed.  A copy of the string is made, so subsequent
               modification of "line" does not affect parsing.  "rsfp", if
               non-null, provides an input stream from which code will be read
               to be parsed.  If both are non-null, the code in "line" comes
               first and must consist of complete lines of input, and "rsfp"
               supplies the remainder of the source.

               The "flags" parameter is reserved for future use.  Currently it
               is only used by perl internally, so extensions should always
               pass zero.

                       void    lex_start(SV *line, PerlIO *rsfp, U32 flags)

       lex_stuff_pv
               NOTE: this function is experimental and may change or be
               removed without notice.

               Insert characters into the lexer buffer ("PL_parser->linestr"),
               immediately after the current lexing point
               ("PL_parser->bufptr"), reallocating the buffer if necessary.
               This means that lexing code that runs later will see the
               characters as if they had appeared in the input.  It is not
               recommended to do this as part of normal parsing, and most uses
               of this facility run the risk of the inserted characters being
               interpreted in an unintended manner.

               The string to be inserted is represented by octets starting at
               "pv" and continuing to the first nul.  These octets are
               interpreted as either UTF-8 or Latin-1, according to whether
               the "LEX_STUFF_UTF8" flag is set in "flags".  The characters
               are recoded for the lexer buffer, according to how the buffer
               is currently being interpreted ("lex_bufutf8").  If it is not
               convenient to nul-terminate a string to be inserted, the
               "lex_stuff_pvn" function is more appropriate.

                       void    lex_stuff_pv(const char *pv, U32 flags)

       lex_stuff_pvn
               NOTE: this function is experimental and may change or be
               removed without notice.

               Insert characters into the lexer buffer ("PL_parser->linestr"),
               immediately after the current lexing point
               ("PL_parser->bufptr"), reallocating the buffer if necessary.
               This means that lexing code that runs later will see the
               characters as if they had appeared in the input.  It is not
               recommended to do this as part of normal parsing, and most uses
               of this facility run the risk of the inserted characters being
               interpreted in an unintended manner.

               The string to be inserted is represented by "len" octets
               starting at "pv".  These octets are interpreted as either UTF-8
               or Latin-1, according to whether the "LEX_STUFF_UTF8" flag is
               set in "flags".  The characters are recoded for the lexer
               buffer, according to how the buffer is currently being
               interpreted ("lex_bufutf8").  If a string to be inserted is
               available as a Perl scalar, the "lex_stuff_sv" function is more
               convenient.

                       void    lex_stuff_pvn(const char *pv, STRLEN len,
                                             U32 flags)

       lex_stuff_pvs
               NOTE: this function is experimental and may change or be
               removed without notice.

               Like "lex_stuff_pvn", but takes a literal string instead of a
               string/length pair.

                       void    lex_stuff_pvs("literal string" pv, U32 flags)

       lex_stuff_sv
               NOTE: this function is experimental and may change or be
               removed without notice.

               Insert characters into the lexer buffer ("PL_parser->linestr"),
               immediately after the current lexing point
               ("PL_parser->bufptr"), reallocating the buffer if necessary.
               This means that lexing code that runs later will see the
               characters as if they had appeared in the input.  It is not
               recommended to do this as part of normal parsing, and most uses
               of this facility run the risk of the inserted characters being
               interpreted in an unintended manner.

               The string to be inserted is the string value of "sv".  The
               characters are recoded for the lexer buffer, according to how
               the buffer is currently being interpreted ("lex_bufutf8").  If
               a string to be inserted is not already a Perl scalar, the
               "lex_stuff_pvn" function avoids the need to construct a scalar.

                       void    lex_stuff_sv(SV *sv, U32 flags)

       lex_unstuff
               NOTE: this function is experimental and may change or be
               removed without notice.

               Discards text about to be lexed, from "PL_parser->bufptr" up to
               "ptr".  Text following "ptr" will be moved, and the buffer
               shortened.  This hides the discarded text from any lexing code
               that runs later, as if the text had never appeared.

               This is not the normal way to consume lexed text.  For that,
               use "lex_read_to".

                       void    lex_unstuff(char *ptr)

       parse_arithexpr
               NOTE: this function is experimental and may change or be
               removed without notice.

               Parse a Perl arithmetic expression.  This may contain operators
               of precedence down to the bit shift operators.  The expression
               must be followed (and thus terminated) either by a comparison
               or lower-precedence operator or by something that would
               normally terminate an expression such as semicolon.  If "flags"
               has the "PARSE_OPTIONAL" bit set, then the expression is
               optional, otherwise it is mandatory.  It is up to the caller to
               ensure that the dynamic parser state ("PL_parser" et al) is
               correctly set to reflect the source of the code to be parsed
               and the lexical context for the expression.

               The op tree representing the expression is returned.  If an
               optional expression is absent, a null pointer is returned,
               otherwise the pointer will be non-null.

               If an error occurs in parsing or compilation, in most cases a
               valid op tree is returned anyway.  The error is reflected in
               the parser state, normally resulting in a single exception at
               the top level of parsing which covers all the compilation
               errors that occurred.  Some compilation errors, however, will
               throw an exception immediately.

                       OP *    parse_arithexpr(U32 flags)

       parse_barestmt
               NOTE: this function is experimental and may change or be
               removed without notice.

               Parse a single unadorned Perl statement.  This may be a normal
               imperative statement or a declaration that has compile-time
               effect.  It does not include any label or other affixture.  It
               is up to the caller to ensure that the dynamic parser state
               ("PL_parser" et al) is correctly set to reflect the source of
               the code to be parsed and the lexical context for the
               statement.

               The op tree representing the statement is returned.  This may
               be a null pointer if the statement is null, for example if it
               was actually a subroutine definition (which has compile-time
               side effects).  If not null, it will be ops directly
               implementing the statement, suitable to pass to "newSTATEOP".
               It will not normally include a "nextstate" or equivalent op
               (except for those embedded in a scope contained entirely within
               the statement).

               If an error occurs in parsing or compilation, in most cases a
               valid op tree (most likely null) is returned anyway.  The error
               is reflected in the parser state, normally resulting in a
               single exception at the top level of parsing which covers all
               the compilation errors that occurred.  Some compilation errors,
               however, will throw an exception immediately.

               The "flags" parameter is reserved for future use, and must
               always be zero.

                       OP *    parse_barestmt(U32 flags)

       parse_block
               NOTE: this function is experimental and may change or be
               removed without notice.

               Parse a single complete Perl code block.  This consists of an
               opening brace, a sequence of statements, and a closing brace.
               The block constitutes a lexical scope, so "my" variables and
               various compile-time effects can be contained within it.  It is
               up to the caller to ensure that the dynamic parser state
               ("PL_parser" et al) is correctly set to reflect the source of
               the code to be parsed and the lexical context for the
               statement.

               The op tree representing the code block is returned.  This is
               always a real op, never a null pointer.  It will normally be a
               "lineseq" list, including "nextstate" or equivalent ops.  No
               ops to construct any kind of runtime scope are included by
               virtue of it being a block.

               If an error occurs in parsing or compilation, in most cases a
               valid op tree (most likely null) is returned anyway.  The error
               is reflected in the parser state, normally resulting in a
               single exception at the top level of parsing which covers all
               the compilation errors that occurred.  Some compilation errors,
               however, will throw an exception immediately.

               The "flags" parameter is reserved for future use, and must
               always be zero.

                       OP *    parse_block(U32 flags)

       parse_fullexpr
               NOTE: this function is experimental and may change or be
               removed without notice.

               Parse a single complete Perl expression.  This allows the full
               expression grammar, including the lowest-precedence operators
               such as "or".  The expression must be followed (and thus
               terminated) by a token that an expression would normally be
               terminated by: end-of-file, closing bracketing punctuation,
               semicolon, or one of the keywords that signals a postfix
               expression-statement modifier.  If "flags" has the
               "PARSE_OPTIONAL" bit set, then the expression is optional,
               otherwise it is mandatory.  It is up to the caller to ensure
               that the dynamic parser state ("PL_parser" et al) is correctly
               set to reflect the source of the code to be parsed and the
               lexical context for the expression.

               The op tree representing the expression is returned.  If an
               optional expression is absent, a null pointer is returned,
               otherwise the pointer will be non-null.

               If an error occurs in parsing or compilation, in most cases a
               valid op tree is returned anyway.  The error is reflected in
               the parser state, normally resulting in a single exception at
               the top level of parsing which covers all the compilation
               errors that occurred.  Some compilation errors, however, will
               throw an exception immediately.

                       OP *    parse_fullexpr(U32 flags)

       parse_fullstmt
               NOTE: this function is experimental and may change or be
               removed without notice.

               Parse a single complete Perl statement.  This may be a normal
               imperative statement or a declaration that has compile-time
               effect, and may include optional labels.  It is up to the
               caller to ensure that the dynamic parser state ("PL_parser" et
               al) is correctly set to reflect the source of the code to be
               parsed and the lexical context for the statement.

               The op tree representing the statement is returned.  This may
               be a null pointer if the statement is null, for example if it
               was actually a subroutine definition (which has compile-time
               side effects).  If not null, it will be the result of a
               "newSTATEOP" call, normally including a "nextstate" or
               equivalent op.

               If an error occurs in parsing or compilation, in most cases a
               valid op tree (most likely null) is returned anyway.  The error
               is reflected in the parser state, normally resulting in a
               single exception at the top level of parsing which covers all
               the compilation errors that occurred.  Some compilation errors,
               however, will throw an exception immediately.

               The "flags" parameter is reserved for future use, and must
               always be zero.

                       OP *    parse_fullstmt(U32 flags)

       parse_label
               NOTE: this function is experimental and may change or be
               removed without notice.

               Parse a single label, possibly optional, of the type that may
               prefix a Perl statement.  It is up to the caller to ensure that
               the dynamic parser state ("PL_parser" et al) is correctly set
               to reflect the source of the code to be parsed.  If "flags" has
               the "PARSE_OPTIONAL" bit set, then the label is optional,
               otherwise it is mandatory.

               The name of the label is returned in the form of a fresh
               scalar.  If an optional label is absent, a null pointer is
               returned.

               If an error occurs in parsing, which can only occur if the
               label is mandatory, a valid label is returned anyway.  The
               error is reflected in the parser state, normally resulting in a
               single exception at the top level of parsing which covers all
               the compilation errors that occurred.

                       SV *    parse_label(U32 flags)

       parse_listexpr
               NOTE: this function is experimental and may change or be
               removed without notice.

               Parse a Perl list expression.  This may contain operators of
               precedence down to the comma operator.  The expression must be
               followed (and thus terminated) either by a low-precedence logic
               operator such as "or" or by something that would normally
               terminate an expression such as semicolon.  If "flags" has the
               "PARSE_OPTIONAL" bit set, then the expression is optional,
               otherwise it is mandatory.  It is up to the caller to ensure
               that the dynamic parser state ("PL_parser" et al) is correctly
               set to reflect the source of the code to be parsed and the
               lexical context for the expression.

               The op tree representing the expression is returned.  If an
               optional expression is absent, a null pointer is returned,
               otherwise the pointer will be non-null.

               If an error occurs in parsing or compilation, in most cases a
               valid op tree is returned anyway.  The error is reflected in
               the parser state, normally resulting in a single exception at
               the top level of parsing which covers all the compilation
               errors that occurred.  Some compilation errors, however, will
               throw an exception immediately.

                       OP *    parse_listexpr(U32 flags)

       parse_stmtseq
               NOTE: this function is experimental and may change or be
               removed without notice.

               Parse a sequence of zero or more Perl statements.  These may be
               normal imperative statements, including optional labels, or
               declarations that have compile-time effect, or any mixture
               thereof.  The statement sequence ends when a closing brace or
               end-of-file is encountered in a place where a new statement
               could have validly started.  It is up to the caller to ensure
               that the dynamic parser state ("PL_parser" et al) is correctly
               set to reflect the source of the code to be parsed and the
               lexical context for the statements.

               The op tree representing the statement sequence is returned.
               This may be a null pointer if the statements were all null, for
               example if there were no statements or if there were only
               subroutine definitions (which have compile-time side effects).
               If not null, it will be a "lineseq" list, normally including
               "nextstate" or equivalent ops.

               If an error occurs in parsing or compilation, in most cases a
               valid op tree is returned anyway.  The error is reflected in
               the parser state, normally resulting in a single exception at
               the top level of parsing which covers all the compilation
               errors that occurred.  Some compilation errors, however, will
               throw an exception immediately.

               The "flags" parameter is reserved for future use, and must
               always be zero.

                       OP *    parse_stmtseq(U32 flags)

       parse_termexpr
               NOTE: this function is experimental and may change or be
               removed without notice.

               Parse a Perl term expression.  This may contain operators of
               precedence down to the assignment operators.  The expression
               must be followed (and thus terminated) either by a comma or
               lower-precedence operator or by something that would normally
               terminate an expression such as semicolon.  If "flags" has the
               "PARSE_OPTIONAL" bit set, then the expression is optional,
               otherwise it is mandatory.  It is up to the caller to ensure
               that the dynamic parser state ("PL_parser" et al) is correctly
               set to reflect the source of the code to be parsed and the
               lexical context for the expression.

               The op tree representing the expression is returned.  If an
               optional expression is absent, a null pointer is returned,
               otherwise the pointer will be non-null.

               If an error occurs in parsing or compilation, in most cases a
               valid op tree is returned anyway.  The error is reflected in
               the parser state, normally resulting in a single exception at
               the top level of parsing which covers all the compilation
               errors that occurred.  Some compilation errors, however, will
               throw an exception immediately.

                       OP *    parse_termexpr(U32 flags)

       PL_parser
               Pointer to a structure encapsulating the state of the parsing
               operation currently in progress.  The pointer can be locally
               changed to perform a nested parse without interfering with the
               state of an outer parse.  Individual members of "PL_parser"
               have their own documentation.

       PL_parser->bufend
               NOTE: this function is experimental and may change or be
               removed without notice.

               Direct pointer to the end of the chunk of text currently being
               lexed, the end of the lexer buffer.  This is equal to
               "SvPVX(PL_parser->linestr) + SvCUR(PL_parser->linestr)".  A
               "NUL" character (zero octet) is always located at the end of
               the buffer, and does not count as part of the buffer's
               contents.

       PL_parser->bufptr
               NOTE: this function is experimental and may change or be
               removed without notice.

               Points to the current position of lexing inside the lexer
               buffer.  Characters around this point may be freely examined,
               within the range delimited by "SvPVX("PL_parser->linestr")" and
               "PL_parser->bufend".  The octets of the buffer may be intended
               to be interpreted as either UTF-8 or Latin-1, as indicated by
               "lex_bufutf8".

               Lexing code (whether in the Perl core or not) moves this
               pointer past the characters that it consumes.  It is also
               expected to perform some bookkeeping whenever a newline
               character is consumed.  This movement can be more conveniently
               performed by the function "lex_read_to", which handles newlines
               appropriately.

               Interpretation of the buffer's octets can be abstracted out by
               using the slightly higher-level functions "lex_peek_unichar"
               and "lex_read_unichar".

       PL_parser->linestart
               NOTE: this function is experimental and may change or be
               removed without notice.

               Points to the start of the current line inside the lexer
               buffer.  This is useful for indicating at which column an error
               occurred, and not much else.  This must be updated by any
               lexing code that consumes a newline; the function "lex_read_to"
               handles this detail.

       PL_parser->linestr
               NOTE: this function is experimental and may change or be
               removed without notice.

               Buffer scalar containing the chunk currently under
               consideration of the text currently being lexed.  This is
               always a plain string scalar (for which "SvPOK" is true).  It
               is not intended to be used as a scalar by normal scalar means;
               instead refer to the buffer directly by the pointer variables
               described below.

               The lexer maintains various "char*" pointers to things in the
               "PL_parser->linestr" buffer.  If "PL_parser->linestr" is ever
               reallocated, all of these pointers must be updated.  Don't
               attempt to do this manually, but rather use "lex_grow_linestr"
               if you need to reallocate the buffer.

               The content of the text chunk in the buffer is commonly exactly
               one complete line of input, up to and including a newline
               terminator, but there are situations where it is otherwise.
               The octets of the buffer may be intended to be interpreted as
               either UTF-8 or Latin-1.  The function "lex_bufutf8" tells you
               which.  Do not use the "SvUTF8" flag on this scalar, which may
               disagree with it.

               For direct examination of the buffer, the variable
               "PL_parser->bufend" points to the end of the buffer.  The
               current lexing position is pointed to by "PL_parser->bufptr".
               Direct use of these pointers is usually preferable to
               examination of the scalar through normal scalar means.

       wrap_keyword_plugin
               NOTE: this function is experimental and may change or be
               removed without notice.

               Puts a C function into the chain of keyword plugins.  This is
               the preferred way to manipulate the "PL_keyword_plugin"
               variable.  "new_plugin" is a pointer to the C function that is
               to be added to the keyword plugin chain, and "old_plugin_p"
               points to the storage location where a pointer to the next
               function in the chain will be stored.  The value of
               "new_plugin" is written into the "PL_keyword_plugin" variable,
               while the value previously stored there is written to
               *old_plugin_p.

               "PL_keyword_plugin" is global to an entire process, and a
               module wishing to hook keyword parsing may find itself invoked
               more than once per process, typically in different threads.  To
               handle that situation, this function is idempotent.  The
               location *old_plugin_p must initially (once per process)
               contain a null pointer.  A C variable of static duration
               (declared at file scope, typically also marked "static" to give
               it internal linkage) will be implicitly initialised
               appropriately, if it does not have an explicit initialiser.
               This function will only actually modify the plugin chain if it
               finds *old_plugin_p to be null.  This function is also thread
               safe on the small scale.  It uses appropriate locking to avoid
               race conditions in accessing "PL_keyword_plugin".

               When this function is called, the function referenced by
               "new_plugin" must be ready to be called, except for
               *old_plugin_p being unfilled.  In a threading situation,
               "new_plugin" may be called immediately, even before this
               function has returned.  *old_plugin_p will always be
               appropriately set before "new_plugin" is called.  If
               "new_plugin" decides not to do anything special with the
               identifier that it is given (which is the usual case for most
               calls to a keyword plugin), it must chain the plugin function
               referenced by *old_plugin_p.

               Taken all together, XS code to install a keyword plugin should
               typically look something like this:

                   static Perl_keyword_plugin_t next_keyword_plugin;
                   static OP *my_keyword_plugin(pTHX_
                       char *keyword_plugin, STRLEN keyword_len, OP **op_ptr)
                   {
                       if (memEQs(keyword_ptr, keyword_len,
                                  "my_new_keyword")) {
                           ...
                       } else {
                           return next_keyword_plugin(aTHX_
                               keyword_ptr, keyword_len, op_ptr);
                       }
                   }
                   BOOT:
                       wrap_keyword_plugin(my_keyword_plugin,
                                           &next_keyword_plugin);

               Direct access to "PL_keyword_plugin" should be avoided.

                       void    wrap_keyword_plugin(
                                   Perl_keyword_plugin_t new_plugin,
                                   Perl_keyword_plugin_t *old_plugin_p
                               )

Locale-related functions and macros
       DECLARATION_FOR_LC_NUMERIC_MANIPULATION
               This macro should be used as a statement.  It declares a
               private variable (whose name begins with an underscore) that is
               needed by the other macros in this section.  Failing to include
               this correctly should lead to a syntax error.  For
               compatibility with C89 C compilers it should be placed in a
               block before any executable statements.

                       void    DECLARATION_FOR_LC_NUMERIC_MANIPULATION

       Perl_langinfo
               This is an (almost) drop-in replacement for the system
               nl_langinfo(3), taking the same "item" parameter values, and
               returning the same information.  But it is more thread-safe
               than regular "nl_langinfo()", and hides the quirks of Perl's
               locale handling from your code, and can be used on systems that
               lack a native "nl_langinfo".

               Expanding on these:

               o   The reason it isn't quite a drop-in replacement is actually
                   an advantage.  The only difference is that it returns
                   "constchar*", whereas plain "nl_langinfo()" returns
                   "char*", but you are (only by documentation) forbidden to
                   write into the buffer.  By declaring this "const", the
                   compiler enforces this restriction, so if it is violated,
                   you know at compilation time, rather than getting segfaults
                   at runtime.

               o   It delivers the correct results for the "RADIXCHAR" and
                   "THOUSEP" items, without you having to write extra code.
                   The reason for the extra code would be because these are
                   from the "LC_NUMERIC" locale category, which is normally
                   kept set by Perl so that the radix is a dot, and the
                   separator is the empty string, no matter what the
                   underlying locale is supposed to be, and so to get the
                   expected results, you have to temporarily toggle into the
                   underlying locale, and later toggle back.  (You could use
                   plain "nl_langinfo" and
                   "STORE_LC_NUMERIC_FORCE_TO_UNDERLYING" for this but then
                   you wouldn't get the other advantages of "Perl_langinfo()";
                   not keeping "LC_NUMERIC" in the C (or equivalent) locale
                   would break a lot of CPAN, which is expecting the radix
                   (decimal point) character to be a dot.)

               o   The system function it replaces can have its static return
                   buffer trashed, not only by a subesequent call to that
                   function, but by a "freelocale", "setlocale", or other
                   locale change.  The returned buffer of this function is not
                   changed until the next call to it, so the buffer is never
                   in a trashed state.

               o   Its return buffer is per-thread, so it also is never
                   overwritten by a call to this function from another thread;
                   unlike the function it replaces.

               o   But most importantly, it works on systems that don't have
                   "nl_langinfo", such as Windows, hence makes your code more
                   portable.  Of the fifty-some possible items specified by
                   the POSIX 2008 standard,
                   <http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/langinfo.h.html>,
                   only one is completely unimplemented, though on non-Windows
                   platforms, another significant one is also not
                   implemented).  It uses various techniques to recover the
                   other items, including calling localeconv(3), and
                   strftime(3), both of which are specified in C89, so should
                   be always be available.  Later "strftime()" versions have
                   additional capabilities; "" is returned for those not
                   available on your system.

                   It is important to note that when called with an item that
                   is recovered by using "localeconv", the buffer from any
                   previous explicit call to "localeconv" will be overwritten.
                   This means you must save that buffer's contents if you need
                   to access them after a call to this function.  (But note
                   that you might not want to be using "localeconv()" directly
                   anyway, because of issues like the ones listed in the
                   second item of this list (above) for "RADIXCHAR" and
                   "THOUSEP".  You can use the methods given in perlcall to
                   call "localeconv" in POSIX and avoid all the issues, but
                   then you have a hash to unpack).

                   The details for those items which may deviate from what
                   this emulation returns and what a native "nl_langinfo()"
                   would return are specified in I18N::Langinfo.

               When using "Perl_langinfo" on systems that don't have a native
               "nl_langinfo()", you must

                #include "perl_langinfo.h"

               before the "perl.h" "#include".  You can replace your
               "langinfo.h" "#include" with this one.  (Doing it this way
               keeps out the symbols that plain "langinfo.h" would try to
               import into the namespace for code that doesn't need it.)

               The original impetus for "Perl_langinfo()" was so that code
               that needs to find out the current currency symbol, floating
               point radix character, or digit grouping separator can use, on
               all systems, the simpler and more thread-friendly "nl_langinfo"
               API instead of localeconv(3) which is a pain to make thread-
               friendly.  For other fields returned by "localeconv", it is
               better to use the methods given in perlcall to call
               "POSIX::localeconv()", which is thread-friendly.

                       const char* Perl_langinfo(const nl_item item)

       Perl_setlocale
               This is an (almost) drop-in replacement for the system
               setlocale(3), taking the same parameters, and returning the
               same information, except that it returns the correct underlying
               "LC_NUMERIC" locale.  Regular "setlocale" will instead return
               "C" if the underlying locale has a non-dot decimal point
               character, or a non-empty thousands separator for displaying
               floating point numbers.  This is because perl keeps that locale
               category such that it has a dot and empty separator, changing
               the locale briefly during the operations where the underlying
               one is required. "Perl_setlocale" knows about this, and
               compensates; regular "setlocale" doesn't.

               Another reason it isn't completely a drop-in replacement is
               that it is declared to return "constchar*", whereas the system
               setlocale omits the "const" (presumably because its API was
               specified long ago, and can't be updated; it is illegal to
               change the information "setlocale" returns; doing so leads to
               segfaults.)

               Finally, "Perl_setlocale" works under all circumstances,
               whereas plain "setlocale" can be completely ineffective on some
               platforms under some configurations.

               "Perl_setlocale" should not be used to change the locale except
               on systems where the predefined variable "${^SAFE_LOCALES}" is
               1.  On some such systems, the system "setlocale()" is
               ineffective, returning the wrong information, and failing to
               actually change the locale.  "Perl_setlocale", however works
               properly in all circumstances.

               The return points to a per-thread static buffer, which is
               overwritten the next time "Perl_setlocale" is called from the
               same thread.

                       const char* Perl_setlocale(const int category,
                                                  const char* locale)

       RESTORE_LC_NUMERIC
               This is used in conjunction with one of the macros
               "STORE_LC_NUMERIC_SET_TO_NEEDED" and
               "STORE_LC_NUMERIC_FORCE_TO_UNDERLYING" to properly restore the
               "LC_NUMERIC" state.

               A call to "DECLARATION_FOR_LC_NUMERIC_MANIPULATION" must have
               been made to declare at compile time a private variable used by
               this macro and the two "STORE" ones.  This macro should be
               called as a single statement, not an expression, but with an
               empty argument list, like this:

                {
                   DECLARATION_FOR_LC_NUMERIC_MANIPULATION;
                    ...
                   RESTORE_LC_NUMERIC();
                    ...
                }

                       void    RESTORE_LC_NUMERIC()

       STORE_LC_NUMERIC_FORCE_TO_UNDERLYING
               This is used by XS code that that is "LC_NUMERIC" locale-aware
               to force the locale for category "LC_NUMERIC" to be what perl
               thinks is the current underlying locale.  (The perl interpreter
               could be wrong about what the underlying locale actually is if
               some C or XS code has called the C library function
               setlocale(3) behind its back; calling "sync_locale" before
               calling this macro will update perl's records.)

               A call to "DECLARATION_FOR_LC_NUMERIC_MANIPULATION" must have
               been made to declare at compile time a private variable used by
               this macro.  This macro should be called as a single statement,
               not an expression, but with an empty argument list, like this:

                {
                   DECLARATION_FOR_LC_NUMERIC_MANIPULATION;
                    ...
                   STORE_LC_NUMERIC_FORCE_TO_UNDERLYING();
                    ...
                   RESTORE_LC_NUMERIC();
                    ...
                }

               The private variable is used to save the current locale state,
               so that the requisite matching call to "RESTORE_LC_NUMERIC" can
               restore it.

               On threaded perls not operating with thread-safe functionality,
               this macro uses a mutex to force a critical section.  Therefore
               the matching RESTORE should be close by, and guaranteed to be
               called.

                       void    STORE_LC_NUMERIC_FORCE_TO_UNDERLYING()

       STORE_LC_NUMERIC_SET_TO_NEEDED
               This is used to help wrap XS or C code that is "LC_NUMERIC"
               locale-aware.  This locale category is generally kept set to a
               locale where the decimal radix character is a dot, and the
               separator between groups of digits is empty.  This is because
               most XS code that reads floating point numbers is expecting
               them to have this syntax.

               This macro makes sure the current "LC_NUMERIC" state is set
               properly, to be aware of locale if the call to the XS or C code
               from the Perl program is from within the scope of a
               "uselocale"; or to ignore locale if the call is instead from
               outside such scope.

               This macro is the start of wrapping the C or XS code; the wrap
               ending is done by calling the "RESTORE_LC_NUMERIC" macro after
               the operation.  Otherwise the state can be changed that will
               adversely affect other XS code.

               A call to "DECLARATION_FOR_LC_NUMERIC_MANIPULATION" must have
               been made to declare at compile time a private variable used by
               this macro.  This macro should be called as a single statement,
               not an expression, but with an empty argument list, like this:

                {
                   DECLARATION_FOR_LC_NUMERIC_MANIPULATION;
                    ...
                   STORE_LC_NUMERIC_SET_TO_NEEDED();
                    ...
                   RESTORE_LC_NUMERIC();
                    ...
                }

               On threaded perls not operating with thread-safe functionality,
               this macro uses a mutex to force a critical section.  Therefore
               the matching RESTORE should be close by, and guaranteed to be
               called.

                       void    STORE_LC_NUMERIC_SET_TO_NEEDED()

       switch_to_global_locale
               On systems without locale support, or on typical single-
               threaded builds, or on platforms that do not support per-thread
               locale operations, this function does nothing.  On such systems
               that do have locale support, only a locale global to the whole
               program is available.

               On multi-threaded builds on systems that do have per-thread
               locale operations, this function converts the thread it is
               running in to use the global locale.  This is for code that has
               not yet or cannot be updated to handle multi-threaded locale
               operation.  As long as only a single thread is so-converted,
               everything works fine, as all the other threads continue to
               ignore the global one, so only this thread looks at it.

               However, on Windows systems this isn't quite true prior to
               Visual Studio 15, at which point Microsoft fixed a bug.  A race
               can occur if you use the following operations on earlier
               Windows platforms:

               POSIX::localeconv
               I18N::Langinfo, items "CRNCYSTR" and "THOUSEP"
               "Perl_langinfo" in perlapi, items "CRNCYSTR" and "THOUSEP"

               The first item is not fixable (except by upgrading to a later
               Visual Studio release), but it would be possible to work around
               the latter two items by using the Windows API functions
               "GetNumberFormat" and "GetCurrencyFormat"; patches welcome.

               Without this function call, threads that use the setlocale(3)
               system function will not work properly, as all the locale-
               sensitive functions will look at the per-thread locale, and
               "setlocale" will have no effect on this thread.

               Perl code should convert to either call "Perl_setlocale" (which
               is a drop-in for the system "setlocale") or use the methods
               given in perlcall to call "POSIX::setlocale".  Either one will
               transparently properly handle all cases of single- vs multi-
               thread, POSIX 2008-supported or not.

               Non-Perl libraries, such as "gtk", that call the system
               "setlocale" can continue to work if this function is called
               before transferring control to the library.

               Upon return from the code that needs to use the global locale,
               "sync_locale()" should be called to restore the safe multi-
               thread operation.

                       void    switch_to_global_locale()

       sync_locale
               "Perl_setlocale" can be used at any time to query or change the
               locale (though changing the locale is antisocial and dangerous
               on multi-threaded systems that don't have multi-thread safe
               locale operations.  (See "Multi-threaded operation" in
               perllocale).  Using the system setlocale(3) should be avoided.
               Nevertheless, certain non-Perl libraries called from XS, such
               as "Gtk" do so, and this can't be changed.  When the locale is
               changed by XS code that didn't use "Perl_setlocale", Perl needs
               to be told that the locale has changed.  Use this function to
               do so, before returning to Perl.

               The return value is a boolean: TRUE if the global locale at the
               time of call was in effect; and FALSE if a per-thread locale
               was in effect.  This can be used by the caller that needs to
               restore things as-they-were to decide whether or not to call
               "Perl_switch_to_global_locale".

                       bool    sync_locale()

Magical Functions
       mg_clear
               Clear something magical that the SV represents.  See
               "sv_magic".

                       int     mg_clear(SV* sv)

       mg_copy Copies the magic from one SV to another.  See "sv_magic".

                       int     mg_copy(SV *sv, SV *nsv, const char *key,
                                       I32 klen)

       mg_find Finds the magic pointer for "type" matching the SV.  See
               "sv_magic".

                       MAGIC*  mg_find(const SV* sv, int type)

       mg_findext
               Finds the magic pointer of "type" with the given "vtbl" for the
               "SV".  See "sv_magicext".

                       MAGIC*  mg_findext(const SV* sv, int type,
                                          const MGVTBL *vtbl)

       mg_free Free any magic storage used by the SV.  See "sv_magic".

                       int     mg_free(SV* sv)

       mg_freeext
               Remove any magic of type "how" using virtual table "vtbl" from
               the SV "sv".  See "sv_magic".

               "mg_freeext(sv, how, NULL)" is equivalent to "mg_free_type(sv,
               how)".

                       void    mg_freeext(SV* sv, int how, const MGVTBL *vtbl)

       mg_free_type
               Remove any magic of type "how" from the SV "sv".  See
               "sv_magic".

                       void    mg_free_type(SV *sv, int how)

       mg_get  Do magic before a value is retrieved from the SV.  The type of
               SV must be >= "SVt_PVMG".  See "sv_magic".

                       int     mg_get(SV* sv)

       mg_length
               DEPRECATED!  It is planned to remove this function from a
               future release of Perl.  Do not use it for new code; remove it
               from existing code.

               Reports on the SV's length in bytes, calling length magic if
               available, but does not set the UTF8 flag on "sv".  It will
               fall back to 'get' magic if there is no 'length' magic, but
               with no indication as to whether it called 'get' magic.  It
               assumes "sv" is a "PVMG" or higher.  Use "sv_len()" instead.

                       U32     mg_length(SV* sv)

       mg_magical
               Turns on the magical status of an SV.  See "sv_magic".

                       void    mg_magical(SV* sv)

       mg_set  Do magic after a value is assigned to the SV.  See "sv_magic".

                       int     mg_set(SV* sv)

       SvGETMAGIC
               Invokes "mg_get" on an SV if it has 'get' magic.  For example,
               this will call "FETCH" on a tied variable.  This macro
               evaluates its argument more than once.

                       void    SvGETMAGIC(SV* sv)

       SvLOCK  Arranges for a mutual exclusion lock to be obtained on "sv" if
               a suitable module has been loaded.

                       void    SvLOCK(SV* sv)

       SvSETMAGIC
               Invokes "mg_set" on an SV if it has 'set' magic.  This is
               necessary after modifying a scalar, in case it is a magical
               variable like $| or a tied variable (it calls "STORE").  This
               macro evaluates its argument more than once.

                       void    SvSETMAGIC(SV* sv)

       SvSetMagicSV
               Like "SvSetSV", but does any set magic required afterwards.

                       void    SvSetMagicSV(SV* dsv, SV* ssv)

       SvSetMagicSV_nosteal
               Like "SvSetSV_nosteal", but does any set magic required
               afterwards.

                       void    SvSetMagicSV_nosteal(SV* dsv, SV* ssv)

       SvSetSV Calls "sv_setsv" if "dsv" is not the same as "ssv".  May
               evaluate arguments more than once.  Does not handle 'set' magic
               on the destination SV.

                       void    SvSetSV(SV* dsv, SV* ssv)

       SvSetSV_nosteal
               Calls a non-destructive version of "sv_setsv" if "dsv" is not
               the same as "ssv".  May evaluate arguments more than once.

                       void    SvSetSV_nosteal(SV* dsv, SV* ssv)

       SvSHARE Arranges for "sv" to be shared between threads if a suitable
               module has been loaded.

                       void    SvSHARE(SV* sv)

       sv_string_from_errnum
               Generates the message string describing an OS error and returns
               it as an SV.  "errnum" must be a value that "errno" could take,
               identifying the type of error.

               If "tgtsv" is non-null then the string will be written into
               that SV (overwriting existing content) and it will be returned.
               If "tgtsv" is a null pointer then the string will be written
               into a new mortal SV which will be returned.

               The message will be taken from whatever locale would be used by
               $!, and will be encoded in the SV in whatever manner would be
               used by $!.  The details of this process are subject to future
               change.  Currently, the message is taken from the C locale by
               default (usually producing an English message), and from the
               currently selected locale when in the scope of the "use locale"
               pragma.  A heuristic attempt is made to decode the message from
               the locale's character encoding, but it will only be decoded as
               either UTF-8 or ISO-8859-1.  It is always correctly decoded in
               a UTF-8 locale, usually in an ISO-8859-1 locale, and never in
               any other locale.

               The SV is always returned containing an actual string, and with
               no other OK bits set.  Unlike $!, a message is even yielded for
               "errnum" zero (meaning success), and if no useful message is
               available then a useless string (currently empty) is returned.

                       SV *    sv_string_from_errnum(int errnum, SV *tgtsv)

       SvUNLOCK
               Releases a mutual exclusion lock on "sv" if a suitable module
               has been loaded.

                       void    SvUNLOCK(SV* sv)

Memory Management
       Copy    The XSUB-writer's interface to the C "memcpy" function.  The
               "src" is the source, "dest" is the destination, "nitems" is the
               number of items, and "type" is the type.  May fail on
               overlapping copies.  See also "Move".

                       void    Copy(void* src, void* dest, int nitems, type)

       CopyD   Like "Copy" but returns "dest".  Useful for encouraging
               compilers to tail-call optimise.

                       void *  CopyD(void* src, void* dest, int nitems, type)

       Move    The XSUB-writer's interface to the C "memmove" function.  The
               "src" is the source, "dest" is the destination, "nitems" is the
               number of items, and "type" is the type.  Can do overlapping
               moves.  See also "Copy".

                       void    Move(void* src, void* dest, int nitems, type)

       MoveD   Like "Move" but returns "dest".  Useful for encouraging
               compilers to tail-call optimise.

                       void *  MoveD(void* src, void* dest, int nitems, type)

       Newx    The XSUB-writer's interface to the C "malloc" function.

               Memory obtained by this should ONLY be freed with "Safefree".

               In 5.9.3, Newx() and friends replace the older New() API, and
               drops the first parameter, x, a debug aid which allowed callers
               to identify themselves.  This aid has been superseded by a new
               build option, PERL_MEM_LOG (see "PERL_MEM_LOG" in
               perlhacktips).  The older API is still there for use in XS
               modules supporting older perls.

                       void    Newx(void* ptr, int nitems, type)

       Newxc   The XSUB-writer's interface to the C "malloc" function, with
               cast.  See also "Newx".

               Memory obtained by this should ONLY be freed with "Safefree".

                       void    Newxc(void* ptr, int nitems, type, cast)

       Newxz   The XSUB-writer's interface to the C "malloc" function.  The
               allocated memory is zeroed with "memzero".  See also "Newx".

               Memory obtained by this should ONLY be freed with "Safefree".

                       void    Newxz(void* ptr, int nitems, type)

       Poison  PoisonWith(0xEF) for catching access to freed memory.

                       void    Poison(void* dest, int nitems, type)

       PoisonFree
               PoisonWith(0xEF) for catching access to freed memory.

                       void    PoisonFree(void* dest, int nitems, type)

       PoisonNew
               PoisonWith(0xAB) for catching access to allocated but
               uninitialized memory.

                       void    PoisonNew(void* dest, int nitems, type)

       PoisonWith
               Fill up memory with a byte pattern (a byte repeated over and
               over again) that hopefully catches attempts to access
               uninitialized memory.

                       void    PoisonWith(void* dest, int nitems, type,
                                          U8 byte)

       Renew   The XSUB-writer's interface to the C "realloc" function.

               Memory obtained by this should ONLY be freed with "Safefree".

                       void    Renew(void* ptr, int nitems, type)

       Renewc  The XSUB-writer's interface to the C "realloc" function, with
               cast.

               Memory obtained by this should ONLY be freed with "Safefree".

                       void    Renewc(void* ptr, int nitems, type, cast)

       Safefree
               The XSUB-writer's interface to the C "free" function.

               This should ONLY be used on memory obtained using "Newx" and
               friends.

                       void    Safefree(void* ptr)

       savepv  Perl's version of "strdup()".  Returns a pointer to a newly
               allocated string which is a duplicate of "pv".  The size of the
               string is determined by "strlen()", which means it may not
               contain embedded "NUL" characters and must have a trailing
               "NUL".  The memory allocated for the new string can be freed
               with the "Safefree()" function.

               On some platforms, Windows for example, all allocated memory
               owned by a thread is deallocated when that thread ends.  So if
               you need that not to happen, you need to use the shared memory
               functions, such as "savesharedpv".

                       char*   savepv(const char* pv)

       savepvn Perl's version of what "strndup()" would be if it existed.
               Returns a pointer to a newly allocated string which is a
               duplicate of the first "len" bytes from "pv", plus a trailing
               "NUL" byte.  The memory allocated for the new string can be
               freed with the "Safefree()" function.

               On some platforms, Windows for example, all allocated memory
               owned by a thread is deallocated when that thread ends.  So if
               you need that not to happen, you need to use the shared memory
               functions, such as "savesharedpvn".

                       char*   savepvn(const char* pv, I32 len)

       savepvs Like "savepvn", but takes a literal string instead of a
               string/length pair.

                       char*   savepvs("literal string" s)

       savesharedpv
               A version of "savepv()" which allocates the duplicate string in
               memory which is shared between threads.

                       char*   savesharedpv(const char* pv)

       savesharedpvn
               A version of "savepvn()" which allocates the duplicate string
               in memory which is shared between threads.  (With the specific
               difference that a "NULL" pointer is not acceptable)

                       char*   savesharedpvn(const char *const pv,
                                             const STRLEN len)

       savesharedpvs
               A version of "savepvs()" which allocates the duplicate string
               in memory which is shared between threads.

                       char*   savesharedpvs("literal string" s)

       savesharedsvpv
               A version of "savesharedpv()" which allocates the duplicate
               string in memory which is shared between threads.

                       char*   savesharedsvpv(SV *sv)

       savesvpv
               A version of "savepv()"/"savepvn()" which gets the string to
               duplicate from the passed in SV using "SvPV()"

               On some platforms, Windows for example, all allocated memory
               owned by a thread is deallocated when that thread ends.  So if
               you need that not to happen, you need to use the shared memory
               functions, such as "savesharedsvpv".

                       char*   savesvpv(SV* sv)

       StructCopy
               This is an architecture-independent macro to copy one structure
               to another.

                       void    StructCopy(type *src, type *dest, type)

       Zero    The XSUB-writer's interface to the C "memzero" function.  The
               "dest" is the destination, "nitems" is the number of items, and
               "type" is the type.

                       void    Zero(void* dest, int nitems, type)

       ZeroD   Like "Zero" but returns dest.  Useful for encouraging compilers
               to tail-call optimise.

                       void *  ZeroD(void* dest, int nitems, type)

Miscellaneous Functions
       dump_c_backtrace
               Dumps the C backtrace to the given "fp".

               Returns true if a backtrace could be retrieved, false if not.

                       bool    dump_c_backtrace(PerlIO* fp, int max_depth,
                                                int skip)

       fbm_compile
               Analyzes the string in order to make fast searches on it using
               "fbm_instr()" -- the Boyer-Moore algorithm.

                       void    fbm_compile(SV* sv, U32 flags)

       fbm_instr
               Returns the location of the SV in the string delimited by "big"
               and "bigend" ("bigend") is the char following the last char).
               It returns "NULL" if the string can't be found.  The "sv" does
               not have to be "fbm_compiled", but the search will not be as
               fast then.

                       char*   fbm_instr(unsigned char* big,
                                         unsigned char* bigend, SV* littlestr,
                                         U32 flags)

       foldEQ  Returns true if the leading "len" bytes of the strings "s1" and
               "s2" are the same case-insensitively; false otherwise.
               Uppercase and lowercase ASCII range bytes match themselves and
               their opposite case counterparts.  Non-cased and non-ASCII
               range bytes match only themselves.

                       I32     foldEQ(const char* a, const char* b, I32 len)

       foldEQ_locale
               Returns true if the leading "len" bytes of the strings "s1" and
               "s2" are the same case-insensitively in the current locale;
               false otherwise.

                       I32     foldEQ_locale(const char* a, const char* b,
                                             I32 len)

       form    Takes a sprintf-style format pattern and conventional (non-SV)
               arguments and returns the formatted string.

                   (char *) Perl_form(pTHX_ const char* pat, ...)

               can be used any place a string (char *) is required:

                   char * s = Perl_form("%d.%d",major,minor);

               Uses a single private buffer so if you want to format several
               strings you must explicitly copy the earlier strings away (and
               free the copies when you are done).

                       char*   form(const char* pat, ...)

       getcwd_sv
               Fill "sv" with current working directory

                       int     getcwd_sv(SV* sv)

       get_c_backtrace_dump
               Returns a SV containing a dump of "depth" frames of the call
               stack, skipping the "skip" innermost ones.  "depth" of 20 is
               usually enough.

               The appended output looks like:

               ...  1   10e004812:0082   Perl_croak   util.c:1716
               /usr/bin/perl 2   10df8d6d2:1d72   perl_parse   perl.c:3975
               /usr/bin/perl ...

               The fields are tab-separated.  The first column is the depth
               (zero being the innermost non-skipped frame).  In the
               hex:offset, the hex is where the program counter was in
               "S_parse_body", and the :offset (might be missing) tells how
               much inside the "S_parse_body" the program counter was.

               The "util.c:1716" is the source code file and line number.

               The /usr/bin/perl is obvious (hopefully).

               Unknowns are "-".  Unknowns can happen unfortunately quite
               easily: if the platform doesn't support retrieving the
               information; if the binary is missing the debug information; if
               the optimizer has transformed the code by for example inlining.

                       SV*     get_c_backtrace_dump(int max_depth, int skip)

       ibcmp   This is a synonym for "(!foldEQ())"

                       I32     ibcmp(const char* a, const char* b, I32 len)

       ibcmp_locale
               This is a synonym for "(!foldEQ_locale())"

                       I32     ibcmp_locale(const char* a, const char* b,
                                            I32 len)

       is_safe_syscall
               Test that the given "pv" doesn't contain any internal "NUL"
               characters.  If it does, set "errno" to "ENOENT", optionally
               warn, and return FALSE.

               Return TRUE if the name is safe.

               Used by the "IS_SAFE_SYSCALL()" macro.

                       bool    is_safe_syscall(const char *pv, STRLEN len,
                                               const char *what,
                                               const char *op_name)

       memEQ   Test two buffers (which may contain embedded "NUL" characters,
               to see if they are equal.  The "len" parameter indicates the
               number of bytes to compare.  Returns zero if equal, or non-zero
               if non-equal.

                       bool    memEQ(char* s1, char* s2, STRLEN len)

       memNE   Test two buffers (which may contain embedded "NUL" characters,
               to see if they are not equal.  The "len" parameter indicates
               the number of bytes to compare.  Returns zero if non-equal, or
               non-zero if equal.

                       bool    memNE(char* s1, char* s2, STRLEN len)

       mess    Take a sprintf-style format pattern and argument list.  These
               are used to generate a string message.  If the message does not
               end with a newline, then it will be extended with some
               indication of the current location in the code, as described
               for "mess_sv".

               Normally, the resulting message is returned in a new mortal SV.
               During global destruction a single SV may be shared between
               uses of this function.

                       SV *    mess(const char *pat, ...)

       mess_sv Expands a message, intended for the user, to include an
               indication of the current location in the code, if the message
               does not already appear to be complete.

               "basemsg" is the initial message or object.  If it is a
               reference, it will be used as-is and will be the result of this
               function.  Otherwise it is used as a string, and if it already
               ends with a newline, it is taken to be complete, and the result
               of this function will be the same string.  If the message does
               not end with a newline, then a segment such as "at foo.pl line
               37" will be appended, and possibly other clauses indicating the
               current state of execution.  The resulting message will end
               with a dot and a newline.

               Normally, the resulting message is returned in a new mortal SV.
               During global destruction a single SV may be shared between
               uses of this function.  If "consume" is true, then the function
               is permitted (but not required) to modify and return "basemsg"
               instead of allocating a new SV.

                       SV *    mess_sv(SV *basemsg, bool consume)

       my_snprintf
               The C library "snprintf" functionality, if available and
               standards-compliant (uses "vsnprintf", actually).  However, if
               the "vsnprintf" is not available, will unfortunately use the
               unsafe "vsprintf" which can overrun the buffer (there is an
               overrun check, but that may be too late).  Consider using
               "sv_vcatpvf" instead, or getting "vsnprintf".

                       int     my_snprintf(char *buffer, const Size_t len,
                                           const char *format, ...)

       my_strlcat
               The C library "strlcat" if available, or a Perl implementation
               of it.  This operates on C "NUL"-terminated strings.

               "my_strlcat()" appends string "src" to the end of "dst".  It
               will append at most "size-strlen(dst)-1" characters.  It will
               then "NUL"-terminate, unless "size" is 0 or the original "dst"
               string was longer than "size" (in practice this should not
               happen as it means that either "size" is incorrect or that
               "dst" is not a proper "NUL"-terminated string).

               Note that "size" is the full size of the destination buffer and
               the result is guaranteed to be "NUL"-terminated if there is
               room.  Note that room for the "NUL" should be included in
               "size".

               The return value is the total length that "dst" would have if
               "size" is sufficiently large.  Thus it is the initial length of
               "dst" plus the length of "src".  If "size" is smaller than the
               return, the excess was not appended.

                       Size_t  my_strlcat(char *dst, const char *src,
                                          Size_t size)

       my_strlcpy
               The C library "strlcpy" if available, or a Perl implementation
               of it.  This operates on C "NUL"-terminated strings.

               "my_strlcpy()" copies up to "size-1" characters from the string
               "src" to "dst", "NUL"-terminating the result if "size" is not
               0.

               The return value is the total length "src" would be if the copy
               completely succeeded.  If it is larger than "size", the excess
               was not copied.

                       Size_t  my_strlcpy(char *dst, const char *src,
                                          Size_t size)

       my_strnlen
               The C library "strnlen" if available, or a Perl implementation
               of it.

               "my_strnlen()" computes the length of the string, up to
               "maxlen" characters.  It will will never attempt to address
               more than "maxlen" characters, making it suitable for use with
               strings that are not guaranteed to be NUL-terminated.

                       Size_t  my_strnlen(const char *str, Size_t maxlen)

       my_vsnprintf
               The C library "vsnprintf" if available and standards-compliant.
               However, if if the "vsnprintf" is not available, will
               unfortunately use the unsafe "vsprintf" which can overrun the
               buffer (there is an overrun check, but that may be too late).
               Consider using "sv_vcatpvf" instead, or getting "vsnprintf".

                       int     my_vsnprintf(char *buffer, const Size_t len,
                                            const char *format, va_list ap)

       ninstr  Find the first (leftmost) occurrence of a sequence of bytes
               within another sequence.  This is the Perl version of
               "strstr()", extended to handle arbitrary sequences, potentially
               containing embedded "NUL" characters ("NUL" is what the initial
               "n" in the function name stands for; some systems have an
               equivalent, "memmem()", but with a somewhat different API).

               Another way of thinking about this function is finding a needle
               in a haystack.  "big" points to the first byte in the haystack.
               "big_end" points to one byte beyond the final byte in the
               haystack.  "little" points to the first byte in the needle.
               "little_end" points to one byte beyond the final byte in the
               needle.  All the parameters must be non-"NULL".

               The function returns "NULL" if there is no occurrence of
               "little" within "big".  If "little" is the empty string, "big"
               is returned.

               Because this function operates at the byte level, and because
               of the inherent characteristics of UTF-8 (or UTF-EBCDIC), it
               will work properly if both the needle and the haystack are
               strings with the same UTF-8ness, but not if the UTF-8ness
               differs.

                       char *  ninstr(char * big, char * bigend, char * little,
                                      char * little_end)

       PERL_SYS_INIT
               Provides system-specific tune up of the C runtime environment
               necessary to run Perl interpreters.  This should be called only
               once, before creating any Perl interpreters.

                       void    PERL_SYS_INIT(int *argc, char*** argv)

       PERL_SYS_INIT3
               Provides system-specific tune up of the C runtime environment
               necessary to run Perl interpreters.  This should be called only
               once, before creating any Perl interpreters.

                       void    PERL_SYS_INIT3(int *argc, char*** argv,
                                              char*** env)

       PERL_SYS_TERM
               Provides system-specific clean up of the C runtime environment
               after running Perl interpreters.  This should be called only
               once, after freeing any remaining Perl interpreters.

                       void    PERL_SYS_TERM()

       quadmath_format_needed
               "quadmath_format_needed()" returns true if the "format" string
               seems to contain at least one non-Q-prefixed "%[efgaEFGA]"
               format specifier, or returns false otherwise.

               The format specifier detection is not complete printf-syntax
               detection, but it should catch most common cases.

               If true is returned, those arguments should in theory be
               processed with "quadmath_snprintf()", but in case there is more
               than one such format specifier (see "quadmath_format_single"),
               and if there is anything else beyond that one (even just a
               single byte), they cannot be processed because
               "quadmath_snprintf()" is very strict, accepting only one format
               spec, and nothing else.  In this case, the code should probably
               fail.

                       bool    quadmath_format_needed(const char* format)

       quadmath_format_single
               "quadmath_snprintf()" is very strict about its "format" string
               and will fail, returning -1, if the format is invalid.  It
               accepts exactly one format spec.

               "quadmath_format_single()" checks that the intended single spec
               looks sane: begins with "%", has only one "%", ends with
               "[efgaEFGA]", and has "Q" before it.  This is not a full
               "printf syntax check", just the basics.

               Returns the format if it is valid, NULL if not.

               "quadmath_format_single()" can and will actually patch in the
               missing "Q", if necessary.  In this case it will return the
               modified copy of the format, which the caller will need to
               free.

               See also "quadmath_format_needed".

                       const char* quadmath_format_single(const char* format)

       READ_XDIGIT
               Returns the value of an ASCII-range hex digit and advances the
               string pointer.  Behaviour is only well defined when
               isXDIGIT(*str) is true.

                       U8      READ_XDIGIT(char str*)

       rninstr Like "ninstr", but instead finds the final (rightmost)
               occurrence of a sequence of bytes within another sequence,
               returning "NULL" if there is no such occurrence.

                       char *  rninstr(char * big, char * bigend,
                                       char * little, char * little_end)

       strEQ   Test two "NUL"-terminated strings to see if they are equal.
               Returns true or false.

                       bool    strEQ(char* s1, char* s2)

       strGE   Test two "NUL"-terminated strings to see if the first, "s1", is
               greater than or equal to the second, "s2".  Returns true or
               false.

                       bool    strGE(char* s1, char* s2)

       strGT   Test two "NUL"-terminated strings to see if the first, "s1", is
               greater than the second, "s2".  Returns true or false.

                       bool    strGT(char* s1, char* s2)

       strLE   Test two "NUL"-terminated strings to see if the first, "s1", is
               less than or equal to the second, "s2".  Returns true or false.

                       bool    strLE(char* s1, char* s2)

       strLT   Test two "NUL"-terminated strings to see if the first, "s1", is
               less than the second, "s2".  Returns true or false.

                       bool    strLT(char* s1, char* s2)

       strNE   Test two "NUL"-terminated strings to see if they are different.
               Returns true or false.

                       bool    strNE(char* s1, char* s2)

       strnEQ  Test two "NUL"-terminated strings to see if they are equal.
               The "len" parameter indicates the number of bytes to compare.
               Returns true or false.  (A wrapper for "strncmp").

                       bool    strnEQ(char* s1, char* s2, STRLEN len)

       strnNE  Test two "NUL"-terminated strings to see if they are different.
               The "len" parameter indicates the number of bytes to compare.
               Returns true or false.  (A wrapper for "strncmp").

                       bool    strnNE(char* s1, char* s2, STRLEN len)

       sv_destroyable
               Dummy routine which reports that object can be destroyed when
               there is no sharing module present.  It ignores its single SV
               argument, and returns 'true'.  Exists to avoid test for a
               "NULL" function pointer and because it could potentially warn
               under some level of strict-ness.

                       bool    sv_destroyable(SV *sv)

       sv_nosharing
               Dummy routine which "shares" an SV when there is no sharing
               module present.  Or "locks" it.  Or "unlocks" it.  In other
               words, ignores its single SV argument.  Exists to avoid test
               for a "NULL" function pointer and because it could potentially
               warn under some level of strict-ness.

                       void    sv_nosharing(SV *sv)

       vmess   "pat" and "args" are a sprintf-style format pattern and
               encapsulated argument list, respectively.  These are used to
               generate a string message.  If the message does not end with a
               newline, then it will be extended with some indication of the
               current location in the code, as described for "mess_sv".

               Normally, the resulting message is returned in a new mortal SV.
               During global destruction a single SV may be shared between
               uses of this function.

                       SV *    vmess(const char *pat, va_list *args)

MRO Functions
       These functions are related to the method resolution order of perl
       classes

       mro_get_linear_isa
               Returns the mro linearisation for the given stash.  By default,
               this will be whatever "mro_get_linear_isa_dfs" returns unless
               some other MRO is in effect for the stash.  The return value is
               a read-only AV*.

               You are responsible for "SvREFCNT_inc()" on the return value if
               you plan to store it anywhere semi-permanently (otherwise it
               might be deleted out from under you the next time the cache is
               invalidated).

                       AV*     mro_get_linear_isa(HV* stash)

       mro_method_changed_in
               Invalidates method caching on any child classes of the given
               stash, so that they might notice the changes in this one.

               Ideally, all instances of "PL_sub_generation++" in perl source
               outside of mro.c should be replaced by calls to this.

               Perl automatically handles most of the common ways a method
               might be redefined.  However, there are a few ways you could
               change a method in a stash without the cache code noticing, in
               which case you need to call this method afterwards:

               1) Directly manipulating the stash HV entries from XS code.

               2) Assigning a reference to a readonly scalar constant into a
               stash entry in order to create a constant subroutine (like
               constant.pm does).

               This same method is available from pure perl via,
               "mro::method_changed_in(classname)".

                       void    mro_method_changed_in(HV* stash)

       mro_register
               Registers a custom mro plugin.  See perlmroapi for details.

                       void    mro_register(const struct mro_alg *mro)

Multicall Functions
       dMULTICALL
               Declare local variables for a multicall.  See "LIGHTWEIGHT
               CALLBACKS" in perlcall.

                               dMULTICALL;

       MULTICALL
               Make a lightweight callback.  See "LIGHTWEIGHT CALLBACKS" in
               perlcall.

                               MULTICALL;

       POP_MULTICALL
               Closing bracket for a lightweight callback.  See "LIGHTWEIGHT
               CALLBACKS" in perlcall.

                               POP_MULTICALL;

       PUSH_MULTICALL
               Opening bracket for a lightweight callback.  See "LIGHTWEIGHT
               CALLBACKS" in perlcall.

                               PUSH_MULTICALL;

Numeric functions
       grok_bin
               converts a string representing a binary number to numeric form.

               On entry "start" and *len give the string to scan, *flags gives
               conversion flags, and "result" should be "NULL" or a pointer to
               an NV.  The scan stops at the end of the string, or the first
               invalid character.  Unless "PERL_SCAN_SILENT_ILLDIGIT" is set
               in *flags, encountering an invalid character will also trigger
               a warning.  On return *len is set to the length of the scanned
               string, and *flags gives output flags.

               If the value is <= "UV_MAX" it is returned as a UV, the output
               flags are clear, and nothing is written to *result.  If the
               value is > "UV_MAX", "grok_bin" returns "UV_MAX", sets
               "PERL_SCAN_GREATER_THAN_UV_MAX" in the output flags, and writes
               the value to *result (or the value is discarded if "result" is
               NULL).

               The binary number may optionally be prefixed with "0b" or "b"
               unless "PERL_SCAN_DISALLOW_PREFIX" is set in *flags on entry.
               If "PERL_SCAN_ALLOW_UNDERSCORES" is set in *flags then the
               binary number may use "_" characters to separate digits.

                       UV      grok_bin(const char* start, STRLEN* len_p,
                                        I32* flags, NV *result)

       grok_hex
               converts a string representing a hex number to numeric form.

               On entry "start" and *len_p give the string to scan, *flags
               gives conversion flags, and "result" should be "NULL" or a
               pointer to an NV.  The scan stops at the end of the string, or
               the first invalid character.  Unless
               "PERL_SCAN_SILENT_ILLDIGIT" is set in *flags, encountering an
               invalid character will also trigger a warning.  On return *len
               is set to the length of the scanned string, and *flags gives
               output flags.

               If the value is <= "UV_MAX" it is returned as a UV, the output
               flags are clear, and nothing is written to *result.  If the
               value is > "UV_MAX", "grok_hex" returns "UV_MAX", sets
               "PERL_SCAN_GREATER_THAN_UV_MAX" in the output flags, and writes
               the value to *result (or the value is discarded if "result" is
               "NULL").

               The hex number may optionally be prefixed with "0x" or "x"
               unless "PERL_SCAN_DISALLOW_PREFIX" is set in *flags on entry.
               If "PERL_SCAN_ALLOW_UNDERSCORES" is set in *flags then the hex
               number may use "_" characters to separate digits.

                       UV      grok_hex(const char* start, STRLEN* len_p,
                                        I32* flags, NV *result)

       grok_infnan
               Helper for "grok_number()", accepts various ways of spelling
               "infinity" or "not a number", and returns one of the following
               flag combinations:

                 IS_NUMBER_INFINITY
                 IS_NUMBER_NAN
                 IS_NUMBER_INFINITY | IS_NUMBER_NEG
                 IS_NUMBER_NAN | IS_NUMBER_NEG
                 0

               possibly |-ed with "IS_NUMBER_TRAILING".

               If an infinity or a not-a-number is recognized, *sp will point
               to one byte past the end of the recognized string.  If the
               recognition fails, zero is returned, and *sp will not move.

                       int     grok_infnan(const char** sp, const char *send)

       grok_number
               Identical to "grok_number_flags()" with "flags" set to zero.

                       int     grok_number(const char *pv, STRLEN len,
                                           UV *valuep)

       grok_number_flags
               Recognise (or not) a number.  The type of the number is
               returned (0 if unrecognised), otherwise it is a bit-ORed
               combination of "IS_NUMBER_IN_UV",
               "IS_NUMBER_GREATER_THAN_UV_MAX", "IS_NUMBER_NOT_INT",
               "IS_NUMBER_NEG", "IS_NUMBER_INFINITY", "IS_NUMBER_NAN" (defined
               in perl.h).

               If the value of the number can fit in a UV, it is returned in
               *valuep.  "IS_NUMBER_IN_UV" will be set to indicate that
               *valuep is valid, "IS_NUMBER_IN_UV" will never be set unless
               *valuep is valid, but *valuep may have been assigned to during
               processing even though "IS_NUMBER_IN_UV" is not set on return.
               If "valuep" is "NULL", "IS_NUMBER_IN_UV" will be set for the
               same cases as when "valuep" is non-"NULL", but no actual
               assignment (or SEGV) will occur.

               "IS_NUMBER_NOT_INT" will be set with "IS_NUMBER_IN_UV" if
               trailing decimals were seen (in which case *valuep gives the
               true value truncated to an integer), and "IS_NUMBER_NEG" if the
               number is negative (in which case *valuep holds the absolute
               value).  "IS_NUMBER_IN_UV" is not set if e notation was used or
               the number is larger than a UV.

               "flags" allows only "PERL_SCAN_TRAILING", which allows for
               trailing non-numeric text on an otherwise successful grok,
               setting "IS_NUMBER_TRAILING" on the result.

                       int     grok_number_flags(const char *pv, STRLEN len,
                                                 UV *valuep, U32 flags)

       grok_numeric_radix
               Scan and skip for a numeric decimal separator (radix).

                       bool    grok_numeric_radix(const char **sp,
                                                  const char *send)

       grok_oct
               converts a string representing an octal number to numeric form.

               On entry "start" and *len give the string to scan, *flags gives
               conversion flags, and "result" should be "NULL" or a pointer to
               an NV.  The scan stops at the end of the string, or the first
               invalid character.  Unless "PERL_SCAN_SILENT_ILLDIGIT" is set
               in *flags, encountering an 8 or 9 will also trigger a warning.
               On return *len is set to the length of the scanned string, and
               *flags gives output flags.

               If the value is <= "UV_MAX" it is returned as a UV, the output
               flags are clear, and nothing is written to *result.  If the
               value is > "UV_MAX", "grok_oct" returns "UV_MAX", sets
               "PERL_SCAN_GREATER_THAN_UV_MAX" in the output flags, and writes
               the value to *result (or the value is discarded if "result" is
               "NULL").

               If "PERL_SCAN_ALLOW_UNDERSCORES" is set in *flags then the
               octal number may use "_" characters to separate digits.

                       UV      grok_oct(const char* start, STRLEN* len_p,
                                        I32* flags, NV *result)

       isinfnan
               "Perl_isinfnan()" is utility function that returns true if the
               NV argument is either an infinity or a "NaN", false otherwise.
               To test in more detail, use "Perl_isinf()" and "Perl_isnan()".

               This is also the logical inverse of Perl_isfinite().

                       bool    isinfnan(NV nv)

       my_strtod
               This function is equivalent to the libc strtod() function, and
               is available even on platforms that lack plain strtod().  Its
               return value is the best available precision depending on
               platform capabilities and Configure options.

               It properly handles the locale radix character, meaning it
               expects a dot except when called from within the scope of
               "uselocale", in which case the radix character should be that
               specified by the current locale.

               The synonym Strod() may be used instead.

                       NV      my_strtod(const char * const s, char ** e)

       Perl_signbit
               NOTE: this function is experimental and may change or be
               removed without notice.

               Return a non-zero integer if the sign bit on an NV is set, and
               0 if it is not.

               If Configure detects this system has a "signbit()" that will
               work with our NVs, then we just use it via the "#define" in
               perl.h.  Otherwise, fall back on this implementation.  The main
               use of this function is catching "-0.0".

               "Configure" notes:  This function is called 'Perl_signbit'
               instead of a plain 'signbit' because it is easy to imagine a
               system having a "signbit()" function or macro that doesn't
               happen to work with our particular choice of NVs.  We shouldn't
               just re-"#define" "signbit" as "Perl_signbit" and expect the
               standard system headers to be happy.  Also, this is a no-
               context function (no "pTHX_") because "Perl_signbit()" is
               usually re-"#defined" in perl.h as a simple macro call to the
               system's "signbit()".  Users should just always call
               "Perl_signbit()".

                       int     Perl_signbit(NV f)

       scan_bin
               For backwards compatibility.  Use "grok_bin" instead.

                       NV      scan_bin(const char* start, STRLEN len,
                                        STRLEN* retlen)

       scan_hex
               For backwards compatibility.  Use "grok_hex" instead.

                       NV      scan_hex(const char* start, STRLEN len,
                                        STRLEN* retlen)

       scan_oct
               For backwards compatibility.  Use "grok_oct" instead.

                       NV      scan_oct(const char* start, STRLEN len,
                                        STRLEN* retlen)

Obsolete backwards compatibility functions
       Some of these are also deprecated.  You can exclude these from your
       compiled Perl by adding this option to Configure:
       "-Accflags='-DNO_MATHOMS'"

       custom_op_desc
               Return the description of a given custom op.  This was once
               used by the "OP_DESC" macro, but is no longer: it has only been
               kept for compatibility, and should not be used.

                       const char * custom_op_desc(const OP *o)

       custom_op_name
               Return the name for a given custom op.  This was once used by
               the "OP_NAME" macro, but is no longer: it has only been kept
               for compatibility, and should not be used.

                       const char * custom_op_name(const OP *o)

       gv_fetchmethod
               See "gv_fetchmethod_autoload".

                       GV*     gv_fetchmethod(HV* stash, const char* name)

       is_utf8_char
               DEPRECATED!  It is planned to remove this function from a
               future release of Perl.  Do not use it for new code; remove it
               from existing code.

               Tests if some arbitrary number of bytes begins in a valid UTF-8
               character.  Note that an INVARIANT (i.e. ASCII on non-EBCDIC
               machines) character is a valid UTF-8 character.  The actual
               number of bytes in the UTF-8 character will be returned if it
               is valid, otherwise 0.

               This function is deprecated due to the possibility that
               malformed input could cause reading beyond the end of the input
               buffer.  Use "isUTF8_CHAR" instead.

                       STRLEN  is_utf8_char(const U8 *s)

       is_utf8_char_buf
               This is identical to the macro "isUTF8_CHAR".

                       STRLEN  is_utf8_char_buf(const U8 *buf,
                                                const U8 *buf_end)

       pack_cat
               The engine implementing "pack()" Perl function.  Note:
               parameters "next_in_list" and "flags" are not used.  This call
               should not be used; use "packlist" instead.

                       void    pack_cat(SV *cat, const char *pat,
                                        const char *patend, SV **beglist,
                                        SV **endlist, SV ***next_in_list,
                                        U32 flags)

       pad_compname_type
               Looks up the type of the lexical variable at position "po" in
               the currently-compiling pad.  If the variable is typed, the
               stash of the class to which it is typed is returned.  If not,
               "NULL" is returned.

                       HV *    pad_compname_type(PADOFFSET po)

       sv_2pvbyte_nolen
               Return a pointer to the byte-encoded representation of the SV.
               May cause the SV to be downgraded from UTF-8 as a side-effect.

               Usually accessed via the "SvPVbyte_nolen" macro.

                       char*   sv_2pvbyte_nolen(SV* sv)

       sv_2pvutf8_nolen
               Return a pointer to the UTF-8-encoded representation of the SV.
               May cause the SV to be upgraded to UTF-8 as a side-effect.

               Usually accessed via the "SvPVutf8_nolen" macro.

                       char*   sv_2pvutf8_nolen(SV* sv)

       sv_2pv_nolen
               Like "sv_2pv()", but doesn't return the length too.  You should
               usually use the macro wrapper "SvPV_nolen(sv)" instead.

                       char*   sv_2pv_nolen(SV* sv)

       sv_catpvn_mg
               Like "sv_catpvn", but also handles 'set' magic.

                       void    sv_catpvn_mg(SV *sv, const char *ptr,
                                            STRLEN len)

       sv_catsv_mg
               Like "sv_catsv", but also handles 'set' magic.

                       void    sv_catsv_mg(SV *dsv, SV *ssv)

       sv_force_normal
               Undo various types of fakery on an SV: if the PV is a shared
               string, make a private copy; if we're a ref, stop refing; if
               we're a glob, downgrade to an "xpvmg".  See also
               "sv_force_normal_flags".

                       void    sv_force_normal(SV *sv)

       sv_iv   A private implementation of the "SvIVx" macro for compilers
               which can't cope with complex macro expressions.  Always use
               the macro instead.

                       IV      sv_iv(SV* sv)

       sv_nolocking
               Dummy routine which "locks" an SV when there is no locking
               module present.  Exists to avoid test for a "NULL" function
               pointer and because it could potentially warn under some level
               of strict-ness.

               "Superseded" by "sv_nosharing()".

                       void    sv_nolocking(SV *sv)

       sv_nounlocking
               Dummy routine which "unlocks" an SV when there is no locking
               module present.  Exists to avoid test for a "NULL" function
               pointer and because it could potentially warn under some level
               of strict-ness.

               "Superseded" by "sv_nosharing()".

                       void    sv_nounlocking(SV *sv)

       sv_nv   A private implementation of the "SvNVx" macro for compilers
               which can't cope with complex macro expressions.  Always use
               the macro instead.

                       NV      sv_nv(SV* sv)

       sv_pv   Use the "SvPV_nolen" macro instead

                       char*   sv_pv(SV *sv)

       sv_pvbyte
               Use "SvPVbyte_nolen" instead.

                       char*   sv_pvbyte(SV *sv)

       sv_pvbyten
               A private implementation of the "SvPVbyte" macro for compilers
               which can't cope with complex macro expressions.  Always use
               the macro instead.

                       char*   sv_pvbyten(SV *sv, STRLEN *lp)

       sv_pvn  A private implementation of the "SvPV" macro for compilers
               which can't cope with complex macro expressions.  Always use
               the macro instead.

                       char*   sv_pvn(SV *sv, STRLEN *lp)

       sv_pvutf8
               Use the "SvPVutf8_nolen" macro instead

                       char*   sv_pvutf8(SV *sv)

       sv_pvutf8n
               A private implementation of the "SvPVutf8" macro for compilers
               which can't cope with complex macro expressions.  Always use
               the macro instead.

                       char*   sv_pvutf8n(SV *sv, STRLEN *lp)

       sv_taint
               Taint an SV.  Use "SvTAINTED_on" instead.

                       void    sv_taint(SV* sv)

       sv_unref
               Unsets the RV status of the SV, and decrements the reference
               count of whatever was being referenced by the RV.  This can
               almost be thought of as a reversal of "newSVrv".  This is
               "sv_unref_flags" with the "flag" being zero.  See "SvROK_off".

                       void    sv_unref(SV* sv)

       sv_usepvn
               Tells an SV to use "ptr" to find its string value.  Implemented
               by calling "sv_usepvn_flags" with "flags" of 0, hence does not
               handle 'set' magic.  See "sv_usepvn_flags".

                       void    sv_usepvn(SV* sv, char* ptr, STRLEN len)

       sv_usepvn_mg
               Like "sv_usepvn", but also handles 'set' magic.

                       void    sv_usepvn_mg(SV *sv, char *ptr, STRLEN len)

       sv_uv   A private implementation of the "SvUVx" macro for compilers
               which can't cope with complex macro expressions.  Always use
               the macro instead.

                       UV      sv_uv(SV* sv)

       unpack_str
               The engine implementing "unpack()" Perl function.  Note:
               parameters "strbeg", "new_s" and "ocnt" are not used.  This
               call should not be used, use "unpackstring" instead.

                       SSize_t unpack_str(const char *pat, const char *patend,
                                          const char *s, const char *strbeg,
                                          const char *strend, char **new_s,
                                          I32 ocnt, U32 flags)

       utf8_to_uvuni
               DEPRECATED!  It is planned to remove this function from a
               future release of Perl.  Do not use it for new code; remove it
               from existing code.

               Returns the Unicode code point of the first character in the
               string "s" which is assumed to be in UTF-8 encoding; "retlen"
               will be set to the length, in bytes, of that character.

               Some, but not all, UTF-8 malformations are detected, and in
               fact, some malformed input could cause reading beyond the end
               of the input buffer, which is one reason why this function is
               deprecated.  The other is that only in extremely limited
               circumstances should the Unicode versus native code point be of
               any interest to you.  See "utf8_to_uvuni_buf" for alternatives.

               If "s" points to one of the detected malformations, and UTF8
               warnings are enabled, zero is returned and *retlen is set (if
               "retlen" doesn't point to NULL) to -1.  If those warnings are
               off, the computed value if well-defined (or the Unicode
               REPLACEMENT CHARACTER, if not) is silently returned, and
               *retlen is set (if "retlen" isn't NULL) so that ("s"+*retlen)
               is the next possible position in "s" that could begin a non-
               malformed character.  See "utf8n_to_uvchr" for details on when
               the REPLACEMENT CHARACTER is returned.

                       UV      utf8_to_uvuni(const U8 *s, STRLEN *retlen)

Optree construction
       newASSIGNOP
               Constructs, checks, and returns an assignment op.  "left" and
               "right" supply the parameters of the assignment; they are
               consumed by this function and become part of the constructed op
               tree.

               If "optype" is "OP_ANDASSIGN", "OP_ORASSIGN", or
               "OP_DORASSIGN", then a suitable conditional optree is
               constructed.  If "optype" is the opcode of a binary operator,
               such as "OP_BIT_OR", then an op is constructed that performs
               the binary operation and assigns the result to the left
               argument.  Either way, if "optype" is non-zero then "flags" has
               no effect.

               If "optype" is zero, then a plain scalar or list assignment is
               constructed.  Which type of assignment it is is automatically
               determined.  "flags" gives the eight bits of "op_flags", except
               that "OPf_KIDS" will be set automatically, and, shifted up
               eight bits, the eight bits of "op_private", except that the bit
               with value 1 or 2 is automatically set as required.

                       OP *    newASSIGNOP(I32 flags, OP *left, I32 optype,
                                           OP *right)

       newBINOP
               Constructs, checks, and returns an op of any binary type.
               "type" is the opcode.  "flags" gives the eight bits of
               "op_flags", except that "OPf_KIDS" will be set automatically,
               and, shifted up eight bits, the eight bits of "op_private",
               except that the bit with value 1 or 2 is automatically set as
               required.  "first" and "last" supply up to two ops to be the
               direct children of the binary op; they are consumed by this
               function and become part of the constructed op tree.

                       OP *    newBINOP(I32 type, I32 flags, OP *first,
                                        OP *last)

       newCONDOP
               Constructs, checks, and returns a conditional-expression
               ("cond_expr") op.  "flags" gives the eight bits of "op_flags",
               except that "OPf_KIDS" will be set automatically, and, shifted
               up eight bits, the eight bits of "op_private", except that the
               bit with value 1 is automatically set.  "first" supplies the
               expression selecting between the two branches, and "trueop" and
               "falseop" supply the branches; they are consumed by this
               function and become part of the constructed op tree.

                       OP *    newCONDOP(I32 flags, OP *first, OP *trueop,
                                         OP *falseop)

       newDEFSVOP
               Constructs and returns an op to access $_.

                       OP *    newDEFSVOP()

       newFOROP
               Constructs, checks, and returns an op tree expressing a
               "foreach" loop (iteration through a list of values).  This is a
               heavyweight loop, with structure that allows exiting the loop
               by "last" and suchlike.

               "sv" optionally supplies the variable that will be aliased to
               each item in turn; if null, it defaults to $_.  "expr" supplies
               the list of values to iterate over.  "block" supplies the main
               body of the loop, and "cont" optionally supplies a "continue"
               block that operates as a second half of the body.  All of these
               optree inputs are consumed by this function and become part of
               the constructed op tree.

               "flags" gives the eight bits of "op_flags" for the "leaveloop"
               op and, shifted up eight bits, the eight bits of "op_private"
               for the "leaveloop" op, except that (in both cases) some bits
               will be set automatically.

                       OP *    newFOROP(I32 flags, OP *sv, OP *expr, OP *block,
                                        OP *cont)

       newGIVENOP
               Constructs, checks, and returns an op tree expressing a "given"
               block.  "cond" supplies the expression to whose value $_ will
               be locally aliased, and "block" supplies the body of the
               "given" construct; they are consumed by this function and
               become part of the constructed op tree.  "defsv_off" must be
               zero (it used to identity the pad slot of lexical $_).

                       OP *    newGIVENOP(OP *cond, OP *block,
                                          PADOFFSET defsv_off)

       newGVOP Constructs, checks, and returns an op of any type that involves
               an embedded reference to a GV.  "type" is the opcode.  "flags"
               gives the eight bits of "op_flags".  "gv" identifies the GV
               that the op should reference; calling this function does not
               transfer ownership of any reference to it.

                       OP *    newGVOP(I32 type, I32 flags, GV *gv)

       newLISTOP
               Constructs, checks, and returns an op of any list type.  "type"
               is the opcode.  "flags" gives the eight bits of "op_flags",
               except that "OPf_KIDS" will be set automatically if required.
               "first" and "last" supply up to two ops to be direct children
               of the list op; they are consumed by this function and become
               part of the constructed op tree.

               For most list operators, the check function expects all the kid
               ops to be present already, so calling "newLISTOP(OP_JOIN, ...)"
               (e.g.) is not appropriate.  What you want to do in that case is
               create an op of type "OP_LIST", append more children to it, and
               then call "op_convert_list".  See "op_convert_list" for more
               information.

                       OP *    newLISTOP(I32 type, I32 flags, OP *first,
                                         OP *last)

       newLOGOP
               Constructs, checks, and returns a logical (flow control) op.
               "type" is the opcode.  "flags" gives the eight bits of
               "op_flags", except that "OPf_KIDS" will be set automatically,
               and, shifted up eight bits, the eight bits of "op_private",
               except that the bit with value 1 is automatically set.  "first"
               supplies the expression controlling the flow, and "other"
               supplies the side (alternate) chain of ops; they are consumed
               by this function and become part of the constructed op tree.

                       OP *    newLOGOP(I32 type, I32 flags, OP *first,
                                        OP *other)

       newLOOPEX
               Constructs, checks, and returns a loop-exiting op (such as
               "goto" or "last").  "type" is the opcode.  "label" supplies the
               parameter determining the target of the op; it is consumed by
               this function and becomes part of the constructed op tree.

                       OP *    newLOOPEX(I32 type, OP *label)

       newLOOPOP
               Constructs, checks, and returns an op tree expressing a loop.
               This is only a loop in the control flow through the op tree; it
               does not have the heavyweight loop structure that allows
               exiting the loop by "last" and suchlike.  "flags" gives the
               eight bits of "op_flags" for the top-level op, except that some
               bits will be set automatically as required.  "expr" supplies
               the expression controlling loop iteration, and "block" supplies
               the body of the loop; they are consumed by this function and
               become part of the constructed op tree.  "debuggable" is
               currently unused and should always be 1.

                       OP *    newLOOPOP(I32 flags, I32 debuggable, OP *expr,
                                         OP *block)

       newMETHOP
               Constructs, checks, and returns an op of method type with a
               method name evaluated at runtime.  "type" is the opcode.
               "flags" gives the eight bits of "op_flags", except that
               "OPf_KIDS" will be set automatically, and, shifted up eight
               bits, the eight bits of "op_private", except that the bit with
               value 1 is automatically set.  "dynamic_meth" supplies an op
               which evaluates method name; it is consumed by this function
               and become part of the constructed op tree.  Supported optypes:
               "OP_METHOD".

                       OP *    newMETHOP(I32 type, I32 flags, OP *first)

       newMETHOP_named
               Constructs, checks, and returns an op of method type with a
               constant method name.  "type" is the opcode.  "flags" gives the
               eight bits of "op_flags", and, shifted up eight bits, the eight
               bits of "op_private".  "const_meth" supplies a constant method
               name; it must be a shared COW string.  Supported optypes:
               "OP_METHOD_NAMED".

                       OP *    newMETHOP_named(I32 type, I32 flags,
                                               SV *const_meth)

       newNULLLIST
               Constructs, checks, and returns a new "stub" op, which
               represents an empty list expression.

                       OP *    newNULLLIST()

       newOP   Constructs, checks, and returns an op of any base type (any
               type that has no extra fields).  "type" is the opcode.  "flags"
               gives the eight bits of "op_flags", and, shifted up eight bits,
               the eight bits of "op_private".

                       OP *    newOP(I32 type, I32 flags)

       newPADOP
               Constructs, checks, and returns an op of any type that involves
               a reference to a pad element.  "type" is the opcode.  "flags"
               gives the eight bits of "op_flags".  A pad slot is
               automatically allocated, and is populated with "sv"; this
               function takes ownership of one reference to it.

               This function only exists if Perl has been compiled to use
               ithreads.

                       OP *    newPADOP(I32 type, I32 flags, SV *sv)

       newPMOP Constructs, checks, and returns an op of any pattern matching
               type.  "type" is the opcode.  "flags" gives the eight bits of
               "op_flags" and, shifted up eight bits, the eight bits of
               "op_private".

                       OP *    newPMOP(I32 type, I32 flags)

       newPVOP Constructs, checks, and returns an op of any type that involves
               an embedded C-level pointer (PV).  "type" is the opcode.
               "flags" gives the eight bits of "op_flags".  "pv" supplies the
               C-level pointer.  Depending on the op type, the memory
               referenced by "pv" may be freed when the op is destroyed.  If
               the op is of a freeing type, "pv" must have been allocated
               using "PerlMemShared_malloc".

                       OP *    newPVOP(I32 type, I32 flags, char *pv)

       newRANGE
               Constructs and returns a "range" op, with subordinate "flip"
               and "flop" ops.  "flags" gives the eight bits of "op_flags" for
               the "flip" op and, shifted up eight bits, the eight bits of
               "op_private" for both the "flip" and "range" ops, except that
               the bit with value 1 is automatically set.  "left" and "right"
               supply the expressions controlling the endpoints of the range;
               they are consumed by this function and become part of the
               constructed op tree.

                       OP *    newRANGE(I32 flags, OP *left, OP *right)

       newSLICEOP
               Constructs, checks, and returns an "lslice" (list slice) op.
               "flags" gives the eight bits of "op_flags", except that
               "OPf_KIDS" will be set automatically, and, shifted up eight
               bits, the eight bits of "op_private", except that the bit with
               value 1 or 2 is automatically set as required.  "listval" and
               "subscript" supply the parameters of the slice; they are
               consumed by this function and become part of the constructed op
               tree.

                       OP *    newSLICEOP(I32 flags, OP *subscript,
                                          OP *listval)

       newSTATEOP
               Constructs a state op (COP).  The state op is normally a
               "nextstate" op, but will be a "dbstate" op if debugging is
               enabled for currently-compiled code.  The state op is populated
               from "PL_curcop" (or "PL_compiling").  If "label" is non-null,
               it supplies the name of a label to attach to the state op; this
               function takes ownership of the memory pointed at by "label",
               and will free it.  "flags" gives the eight bits of "op_flags"
               for the state op.

               If "o" is null, the state op is returned.  Otherwise the state
               op is combined with "o" into a "lineseq" list op, which is
               returned.  "o" is consumed by this function and becomes part of
               the returned op tree.

                       OP *    newSTATEOP(I32 flags, char *label, OP *o)

       newSVOP Constructs, checks, and returns an op of any type that involves
               an embedded SV.  "type" is the opcode.  "flags" gives the eight
               bits of "op_flags".  "sv" gives the SV to embed in the op; this
               function takes ownership of one reference to it.

                       OP *    newSVOP(I32 type, I32 flags, SV *sv)

       newUNOP Constructs, checks, and returns an op of any unary type.
               "type" is the opcode.  "flags" gives the eight bits of
               "op_flags", except that "OPf_KIDS" will be set automatically if
               required, and, shifted up eight bits, the eight bits of
               "op_private", except that the bit with value 1 is automatically
               set.  "first" supplies an optional op to be the direct child of
               the unary op; it is consumed by this function and become part
               of the constructed op tree.

                       OP *    newUNOP(I32 type, I32 flags, OP *first)

       newUNOP_AUX
               Similar to "newUNOP", but creates an "UNOP_AUX" struct instead,
               with "op_aux" initialised to "aux"

                       OP*     newUNOP_AUX(I32 type, I32 flags, OP* first,
                                           UNOP_AUX_item *aux)

       newWHENOP
               Constructs, checks, and returns an op tree expressing a "when"
               block.  "cond" supplies the test expression, and "block"
               supplies the block that will be executed if the test evaluates
               to true; they are consumed by this function and become part of
               the constructed op tree.  "cond" will be interpreted
               DWIMically, often as a comparison against $_, and may be null
               to generate a "default" block.

                       OP *    newWHENOP(OP *cond, OP *block)

       newWHILEOP
               Constructs, checks, and returns an op tree expressing a "while"
               loop.  This is a heavyweight loop, with structure that allows
               exiting the loop by "last" and suchlike.

               "loop" is an optional preconstructed "enterloop" op to use in
               the loop; if it is null then a suitable op will be constructed
               automatically.  "expr" supplies the loop's controlling
               expression.  "block" supplies the main body of the loop, and
               "cont" optionally supplies a "continue" block that operates as
               a second half of the body.  All of these optree inputs are
               consumed by this function and become part of the constructed op
               tree.

               "flags" gives the eight bits of "op_flags" for the "leaveloop"
               op and, shifted up eight bits, the eight bits of "op_private"
               for the "leaveloop" op, except that (in both cases) some bits
               will be set automatically.  "debuggable" is currently unused
               and should always be 1.  "has_my" can be supplied as true to
               force the loop body to be enclosed in its own scope.

                       OP *    newWHILEOP(I32 flags, I32 debuggable,
                                          LOOP *loop, OP *expr, OP *block,
                                          OP *cont, I32 has_my)

Optree Manipulation Functions
       alloccopstash
               NOTE: this function is experimental and may change or be
               removed without notice.

               Available only under threaded builds, this function allocates
               an entry in "PL_stashpad" for the stash passed to it.

                       PADOFFSET alloccopstash(HV *hv)

       block_end
               Handles compile-time scope exit.  "floor" is the savestack
               index returned by "block_start", and "seq" is the body of the
               block.  Returns the block, possibly modified.

                       OP *    block_end(I32 floor, OP *seq)

       block_start
               Handles compile-time scope entry.  Arranges for hints to be
               restored on block exit and also handles pad sequence numbers to
               make lexical variables scope right.  Returns a savestack index
               for use with "block_end".

                       int     block_start(int full)

       ck_entersub_args_list
               Performs the default fixup of the arguments part of an
               "entersub" op tree.  This consists of applying list context to
               each of the argument ops.  This is the standard treatment used
               on a call marked with "&", or a method call, or a call through
               a subroutine reference, or any other call where the callee
               can't be identified at compile time, or a call where the callee
               has no prototype.

                       OP *    ck_entersub_args_list(OP *entersubop)

       ck_entersub_args_proto
               Performs the fixup of the arguments part of an "entersub" op
               tree based on a subroutine prototype.  This makes various
               modifications to the argument ops, from applying context up to
               inserting "refgen" ops, and checking the number and syntactic
               types of arguments, as directed by the prototype.  This is the
               standard treatment used on a subroutine call, not marked with
               "&", where the callee can be identified at compile time and has
               a prototype.

               "protosv" supplies the subroutine prototype to be applied to
               the call.  It may be a normal defined scalar, of which the
               string value will be used.  Alternatively, for convenience, it
               may be a subroutine object (a "CV*" that has been cast to
               "SV*") which has a prototype.  The prototype supplied, in
               whichever form, does not need to match the actual callee
               referenced by the op tree.

               If the argument ops disagree with the prototype, for example by
               having an unacceptable number of arguments, a valid op tree is
               returned anyway.  The error is reflected in the parser state,
               normally resulting in a single exception at the top level of
               parsing which covers all the compilation errors that occurred.
               In the error message, the callee is referred to by the name
               defined by the "namegv" parameter.

                       OP *    ck_entersub_args_proto(OP *entersubop,
                                                      GV *namegv, SV *protosv)

       ck_entersub_args_proto_or_list
               Performs the fixup of the arguments part of an "entersub" op
               tree either based on a subroutine prototype or using default
               list-context processing.  This is the standard treatment used
               on a subroutine call, not marked with "&", where the callee can
               be identified at compile time.

               "protosv" supplies the subroutine prototype to be applied to
               the call, or indicates that there is no prototype.  It may be a
               normal scalar, in which case if it is defined then the string
               value will be used as a prototype, and if it is undefined then
               there is no prototype.  Alternatively, for convenience, it may
               be a subroutine object (a "CV*" that has been cast to "SV*"),
               of which the prototype will be used if it has one.  The
               prototype (or lack thereof) supplied, in whichever form, does
               not need to match the actual callee referenced by the op tree.

               If the argument ops disagree with the prototype, for example by
               having an unacceptable number of arguments, a valid op tree is
               returned anyway.  The error is reflected in the parser state,
               normally resulting in a single exception at the top level of
               parsing which covers all the compilation errors that occurred.
               In the error message, the callee is referred to by the name
               defined by the "namegv" parameter.

                       OP *    ck_entersub_args_proto_or_list(OP *entersubop,
                                                              GV *namegv,
                                                              SV *protosv)

       cv_const_sv
               If "cv" is a constant sub eligible for inlining, returns the
               constant value returned by the sub.  Otherwise, returns "NULL".

               Constant subs can be created with "newCONSTSUB" or as described
               in "Constant Functions" in perlsub.

                       SV*     cv_const_sv(const CV *const cv)

       cv_get_call_checker
               The original form of "cv_get_call_checker_flags", which does
               not return checker flags.  When using a checker function
               returned by this function, it is only safe to call it with a
               genuine GV as its "namegv" argument.

                       void    cv_get_call_checker(CV *cv,
                                                   Perl_call_checker *ckfun_p,
                                                   SV **ckobj_p)

       cv_get_call_checker_flags
               Retrieves the function that will be used to fix up a call to
               "cv".  Specifically, the function is applied to an "entersub"
               op tree for a subroutine call, not marked with "&", where the
               callee can be identified at compile time as "cv".

               The C-level function pointer is returned in *ckfun_p, an SV
               argument for it is returned in *ckobj_p, and control flags are
               returned in *ckflags_p.  The function is intended to be called
               in this manner:

                entersubop = (*ckfun_p)(aTHX_ entersubop, namegv, (*ckobj_p));

               In this call, "entersubop" is a pointer to the "entersub" op,
               which may be replaced by the check function, and "namegv"
               supplies the name that should be used by the check function to
               refer to the callee of the "entersub" op if it needs to emit
               any diagnostics.  It is permitted to apply the check function
               in non-standard situations, such as to a call to a different
               subroutine or to a method call.

               "namegv" may not actually be a GV.  If the
               "CALL_CHECKER_REQUIRE_GV" bit is clear in *ckflags_p, it is
               permitted to pass a CV or other SV instead, anything that can
               be used as the first argument to "cv_name".  If the
               "CALL_CHECKER_REQUIRE_GV" bit is set in *ckflags_p then the
               check function requires "namegv" to be a genuine GV.

               By default, the check function is
               Perl_ck_entersub_args_proto_or_list, the SV parameter is "cv"
               itself, and the "CALL_CHECKER_REQUIRE_GV" flag is clear.  This
               implements standard prototype processing.  It can be changed,
               for a particular subroutine, by "cv_set_call_checker_flags".

               If the "CALL_CHECKER_REQUIRE_GV" bit is set in "gflags" then it
               indicates that the caller only knows about the genuine GV
               version of "namegv", and accordingly the corresponding bit will
               always be set in *ckflags_p, regardless of the check function's
               recorded requirements.  If the "CALL_CHECKER_REQUIRE_GV" bit is
               clear in "gflags" then it indicates the caller knows about the
               possibility of passing something other than a GV as "namegv",
               and accordingly the corresponding bit may be either set or
               clear in *ckflags_p, indicating the check function's recorded
               requirements.

               "gflags" is a bitset passed into "cv_get_call_checker_flags",
               in which only the "CALL_CHECKER_REQUIRE_GV" bit currently has a
               defined meaning (for which see above).  All other bits should
               be clear.

                       void    cv_get_call_checker_flags(
                                   CV *cv, U32 gflags,
                                   Perl_call_checker *ckfun_p, SV **ckobj_p,
                                   U32 *ckflags_p
                               )

       cv_set_call_checker
               The original form of "cv_set_call_checker_flags", which passes
               it the "CALL_CHECKER_REQUIRE_GV" flag for backward-
               compatibility.  The effect of that flag setting is that the
               check function is guaranteed to get a genuine GV as its
               "namegv" argument.

                       void    cv_set_call_checker(CV *cv,
                                                   Perl_call_checker ckfun,
                                                   SV *ckobj)

       cv_set_call_checker_flags
               Sets the function that will be used to fix up a call to "cv".
               Specifically, the function is applied to an "entersub" op tree
               for a subroutine call, not marked with "&", where the callee
               can be identified at compile time as "cv".

               The C-level function pointer is supplied in "ckfun", an SV
               argument for it is supplied in "ckobj", and control flags are
               supplied in "ckflags".  The function should be defined like
               this:

                   STATIC OP * ckfun(pTHX_ OP *op, GV *namegv, SV *ckobj)

               It is intended to be called in this manner:

                   entersubop = ckfun(aTHX_ entersubop, namegv, ckobj);

               In this call, "entersubop" is a pointer to the "entersub" op,
               which may be replaced by the check function, and "namegv"
               supplies the name that should be used by the check function to
               refer to the callee of the "entersub" op if it needs to emit
               any diagnostics.  It is permitted to apply the check function
               in non-standard situations, such as to a call to a different
               subroutine or to a method call.

               "namegv" may not actually be a GV.  For efficiency, perl may
               pass a CV or other SV instead.  Whatever is passed can be used
               as the first argument to "cv_name".  You can force perl to pass
               a GV by including "CALL_CHECKER_REQUIRE_GV" in the "ckflags".

               "ckflags" is a bitset, in which only the
               "CALL_CHECKER_REQUIRE_GV" bit currently has a defined meaning
               (for which see above).  All other bits should be clear.

               The current setting for a particular CV can be retrieved by
               "cv_get_call_checker_flags".

                       void    cv_set_call_checker_flags(
                                   CV *cv, Perl_call_checker ckfun, SV *ckobj,
                                   U32 ckflags
                               )

       LINKLIST
               Given the root of an optree, link the tree in execution order
               using the "op_next" pointers and return the first op executed.
               If this has already been done, it will not be redone, and
               "o->op_next" will be returned.  If "o->op_next" is not already
               set, "o" should be at least an "UNOP".

                       OP*     LINKLIST(OP *o)

       newCONSTSUB
               Behaves like "newCONSTSUB_flags", except that "name" is nul-
               terminated rather than of counted length, and no flags are set.
               (This means that "name" is always interpreted as Latin-1.)

                       CV *    newCONSTSUB(HV *stash, const char *name, SV *sv)

       newCONSTSUB_flags
               Construct a constant subroutine, also performing some
               surrounding jobs.  A scalar constant-valued subroutine is
               eligible for inlining at compile-time, and in Perl code can be
               created by "subFOO(){123}".  Other kinds of constant subroutine
               have other treatment.

               The subroutine will have an empty prototype and will ignore any
               arguments when called.  Its constant behaviour is determined by
               "sv".  If "sv" is null, the subroutine will yield an empty
               list.  If "sv" points to a scalar, the subroutine will always
               yield that scalar.  If "sv" points to an array, the subroutine
               will always yield a list of the elements of that array in list
               context, or the number of elements in the array in scalar
               context.  This function takes ownership of one counted
               reference to the scalar or array, and will arrange for the
               object to live as long as the subroutine does.  If "sv" points
               to a scalar then the inlining assumes that the value of the
               scalar will never change, so the caller must ensure that the
               scalar is not subsequently written to.  If "sv" points to an
               array then no such assumption is made, so it is ostensibly safe
               to mutate the array or its elements, but whether this is really
               supported has not been determined.

               The subroutine will have "CvFILE" set according to "PL_curcop".
               Other aspects of the subroutine will be left in their default
               state.  The caller is free to mutate the subroutine beyond its
               initial state after this function has returned.

               If "name" is null then the subroutine will be anonymous, with
               its "CvGV" referring to an "__ANON__" glob.  If "name" is non-
               null then the subroutine will be named accordingly, referenced
               by the appropriate glob.  "name" is a string of length "len"
               bytes giving a sigilless symbol name, in UTF-8 if "flags" has
               the "SVf_UTF8" bit set and in Latin-1 otherwise.  The name may
               be either qualified or unqualified.  If the name is unqualified
               then it defaults to being in the stash specified by "stash" if
               that is non-null, or to "PL_curstash" if "stash" is null.  The
               symbol is always added to the stash if necessary, with
               "GV_ADDMULTI" semantics.

               "flags" should not have bits set other than "SVf_UTF8".

               If there is already a subroutine of the specified name, then
               the new sub will replace the existing one in the glob.  A
               warning may be generated about the redefinition.

               If the subroutine has one of a few special names, such as
               "BEGIN" or "END", then it will be claimed by the appropriate
               queue for automatic running of phase-related subroutines.  In
               this case the relevant glob will be left not containing any
               subroutine, even if it did contain one before.  Execution of
               the subroutine will likely be a no-op, unless "sv" was a tied
               array or the caller modified the subroutine in some interesting
               way before it was executed.  In the case of "BEGIN", the
               treatment is buggy: the sub will be executed when only half
               built, and may be deleted prematurely, possibly causing a
               crash.

               The function returns a pointer to the constructed subroutine.
               If the sub is anonymous then ownership of one counted reference
               to the subroutine is transferred to the caller.  If the sub is
               named then the caller does not get ownership of a reference.
               In most such cases, where the sub has a non-phase name, the sub
               will be alive at the point it is returned by virtue of being
               contained in the glob that names it.  A phase-named subroutine
               will usually be alive by virtue of the reference owned by the
               phase's automatic run queue.  A "BEGIN" subroutine may have
               been destroyed already by the time this function returns, but
               currently bugs occur in that case before the caller gets
               control.  It is the caller's responsibility to ensure that it
               knows which of these situations applies.

                       CV *    newCONSTSUB_flags(HV *stash, const char *name,
                                                 STRLEN len, U32 flags, SV *sv)

       newXS   Used by "xsubpp" to hook up XSUBs as Perl subs.  "filename"
               needs to be static storage, as it is used directly as CvFILE(),
               without a copy being made.

       op_append_elem
               Append an item to the list of ops contained directly within a
               list-type op, returning the lengthened list.  "first" is the
               list-type op, and "last" is the op to append to the list.
               "optype" specifies the intended opcode for the list.  If
               "first" is not already a list of the right type, it will be
               upgraded into one.  If either "first" or "last" is null, the
               other is returned unchanged.

                       OP *    op_append_elem(I32 optype, OP *first, OP *last)

       op_append_list
               Concatenate the lists of ops contained directly within two
               list-type ops, returning the combined list.  "first" and "last"
               are the list-type ops to concatenate.  "optype" specifies the
               intended opcode for the list.  If either "first" or "last" is
               not already a list of the right type, it will be upgraded into
               one.  If either "first" or "last" is null, the other is
               returned unchanged.

                       OP *    op_append_list(I32 optype, OP *first, OP *last)

       OP_CLASS
               Return the class of the provided OP: that is, which of the *OP
               structures it uses.  For core ops this currently gets the
               information out of "PL_opargs", which does not always
               accurately reflect the type used; in v5.26 onwards, see also
               the function "op_class" which can do a better job of
               determining the used type.

               For custom ops the type is returned from the registration, and
               it is up to the registree to ensure it is accurate.  The value
               returned will be one of the "OA_"* constants from op.h.

                       U32     OP_CLASS(OP *o)

       op_contextualize
               Applies a syntactic context to an op tree representing an
               expression.  "o" is the op tree, and "context" must be
               "G_SCALAR", "G_ARRAY", or "G_VOID" to specify the context to
               apply.  The modified op tree is returned.

                       OP *    op_contextualize(OP *o, I32 context)

       op_convert_list
               Converts "o" into a list op if it is not one already, and then
               converts it into the specified "type", calling its check
               function, allocating a target if it needs one, and folding
               constants.

               A list-type op is usually constructed one kid at a time via
               "newLISTOP", "op_prepend_elem" and "op_append_elem".  Then
               finally it is passed to "op_convert_list" to make it the right
               type.

                       OP *    op_convert_list(I32 type, I32 flags, OP *o)

       OP_DESC Return a short description of the provided OP.

                       const char * OP_DESC(OP *o)

       op_free Free an op.  Only use this when an op is no longer linked to
               from any optree.

                       void    op_free(OP *o)

       OpHAS_SIBLING
               Returns true if "o" has a sibling

                       bool    OpHAS_SIBLING(OP *o)

       OpLASTSIB_set
               Marks "o" as having no further siblings and marks o as having
               the specified parent. See also "OpMORESIB_set" and
               "OpMAYBESIB_set". For a higher-level interface, see
               "op_sibling_splice".

                       void    OpLASTSIB_set(OP *o, OP *parent)

       op_linklist
               This function is the implementation of the "LINKLIST" macro.
               It should not be called directly.

                       OP*     op_linklist(OP *o)

       op_lvalue
               NOTE: this function is experimental and may change or be
               removed without notice.

               Propagate lvalue ("modifiable") context to an op and its
               children.  "type" represents the context type, roughly based on
               the type of op that would do the modifying, although "local()"
               is represented by "OP_NULL", because it has no op type of its
               own (it is signalled by a flag on the lvalue op).

               This function detects things that can't be modified, such as
               "$x+1", and generates errors for them.  For example, "$x+1 = 2"
               would cause it to be called with an op of type "OP_ADD" and a
               "type" argument of "OP_SASSIGN".

               It also flags things that need to behave specially in an lvalue
               context, such as "$$x = 5" which might have to vivify a
               reference in $x.

                       OP *    op_lvalue(OP *o, I32 type)

       OpMAYBESIB_set
               Conditionally does "OpMORESIB_set" or "OpLASTSIB_set" depending
               on whether "sib" is non-null. For a higher-level interface, see
               "op_sibling_splice".

                       void    OpMAYBESIB_set(OP *o, OP *sib, OP *parent)

       OpMORESIB_set
               Sets the sibling of "o" to the non-zero value "sib". See also
               "OpLASTSIB_set" and "OpMAYBESIB_set". For a higher-level
               interface, see "op_sibling_splice".

                       void    OpMORESIB_set(OP *o, OP *sib)

       OP_NAME Return the name of the provided OP.  For core ops this looks up
               the name from the op_type; for custom ops from the op_ppaddr.

                       const char * OP_NAME(OP *o)

       op_null Neutralizes an op when it is no longer needed, but is still
               linked to from other ops.

                       void    op_null(OP *o)

       op_parent
               Returns the parent OP of "o", if it has a parent. Returns
               "NULL" otherwise.

                       OP*     op_parent(OP *o)

       op_prepend_elem
               Prepend an item to the list of ops contained directly within a
               list-type op, returning the lengthened list.  "first" is the op
               to prepend to the list, and "last" is the list-type op.
               "optype" specifies the intended opcode for the list.  If "last"
               is not already a list of the right type, it will be upgraded
               into one.  If either "first" or "last" is null, the other is
               returned unchanged.

                       OP *    op_prepend_elem(I32 optype, OP *first, OP *last)

       op_scope
               NOTE: this function is experimental and may change or be
               removed without notice.

               Wraps up an op tree with some additional ops so that at runtime
               a dynamic scope will be created.  The original ops run in the
               new dynamic scope, and then, provided that they exit normally,
               the scope will be unwound.  The additional ops used to create
               and unwind the dynamic scope will normally be an
               "enter"/"leave" pair, but a "scope" op may be used instead if
               the ops are simple enough to not need the full dynamic scope
               structure.

                       OP *    op_scope(OP *o)

       OpSIBLING
               Returns the sibling of "o", or "NULL" if there is no sibling

                       OP*     OpSIBLING(OP *o)

       op_sibling_splice
               A general function for editing the structure of an existing
               chain of op_sibling nodes.  By analogy with the perl-level
               "splice()" function, allows you to delete zero or more
               sequential nodes, replacing them with zero or more different
               nodes.  Performs the necessary op_first/op_last housekeeping on
               the parent node and op_sibling manipulation on the children.
               The last deleted node will be marked as as the last node by
               updating the op_sibling/op_sibparent or op_moresib field as
               appropriate.

               Note that op_next is not manipulated, and nodes are not freed;
               that is the responsibility of the caller.  It also won't create
               a new list op for an empty list etc; use higher-level functions
               like op_append_elem() for that.

               "parent" is the parent node of the sibling chain. It may passed
               as "NULL" if the splicing doesn't affect the first or last op
               in the chain.

               "start" is the node preceding the first node to be spliced.
               Node(s) following it will be deleted, and ops will be inserted
               after it.  If it is "NULL", the first node onwards is deleted,
               and nodes are inserted at the beginning.

               "del_count" is the number of nodes to delete.  If zero, no
               nodes are deleted.  If -1 or greater than or equal to the
               number of remaining kids, all remaining kids are deleted.

               "insert" is the first of a chain of nodes to be inserted in
               place of the nodes.  If "NULL", no nodes are inserted.

               The head of the chain of deleted ops is returned, or "NULL" if
               no ops were deleted.

               For example:

                   action                    before      after         returns
                   ------                    -----       -----         -------

                                             P           P
                   splice(P, A, 2, X-Y-Z)    |           |             B-C
                                             A-B-C-D     A-X-Y-Z-D

                                             P           P
                   splice(P, NULL, 1, X-Y)   |           |             A
                                             A-B-C-D     X-Y-B-C-D

                                             P           P
                   splice(P, NULL, 3, NULL)  |           |             A-B-C
                                             A-B-C-D     D

                                             P           P
                   splice(P, B, 0, X-Y)      |           |             NULL
                                             A-B-C-D     A-B-X-Y-C-D

               For lower-level direct manipulation of "op_sibparent" and
               "op_moresib", see "OpMORESIB_set", "OpLASTSIB_set",
               "OpMAYBESIB_set".

                       OP*     op_sibling_splice(OP *parent, OP *start,
                                                 int del_count, OP* insert)

       OP_TYPE_IS
               Returns true if the given OP is not a "NULL" pointer and if it
               is of the given type.

               The negation of this macro, "OP_TYPE_ISNT" is also available as
               well as "OP_TYPE_IS_NN" and "OP_TYPE_ISNT_NN" which elide the
               NULL pointer check.

                       bool    OP_TYPE_IS(OP *o, Optype type)

       OP_TYPE_IS_OR_WAS
               Returns true if the given OP is not a NULL pointer and if it is
               of the given type or used to be before being replaced by an OP
               of type OP_NULL.

               The negation of this macro, "OP_TYPE_ISNT_AND_WASNT" is also
               available as well as "OP_TYPE_IS_OR_WAS_NN" and
               "OP_TYPE_ISNT_AND_WASNT_NN" which elide the "NULL" pointer
               check.

                       bool    OP_TYPE_IS_OR_WAS(OP *o, Optype type)

       rv2cv_op_cv
               Examines an op, which is expected to identify a subroutine at
               runtime, and attempts to determine at compile time which
               subroutine it identifies.  This is normally used during Perl
               compilation to determine whether a prototype can be applied to
               a function call.  "cvop" is the op being considered, normally
               an "rv2cv" op.  A pointer to the identified subroutine is
               returned, if it could be determined statically, and a null
               pointer is returned if it was not possible to determine
               statically.

               Currently, the subroutine can be identified statically if the
               RV that the "rv2cv" is to operate on is provided by a suitable
               "gv" or "const" op.  A "gv" op is suitable if the GV's CV slot
               is populated.  A "const" op is suitable if the constant value
               must be an RV pointing to a CV.  Details of this process may
               change in future versions of Perl.  If the "rv2cv" op has the
               "OPpENTERSUB_AMPER" flag set then no attempt is made to
               identify the subroutine statically: this flag is used to
               suppress compile-time magic on a subroutine call, forcing it to
               use default runtime behaviour.

               If "flags" has the bit "RV2CVOPCV_MARK_EARLY" set, then the
               handling of a GV reference is modified.  If a GV was examined
               and its CV slot was found to be empty, then the "gv" op has the
               "OPpEARLY_CV" flag set.  If the op is not optimised away, and
               the CV slot is later populated with a subroutine having a
               prototype, that flag eventually triggers the warning "called
               too early to check prototype".

               If "flags" has the bit "RV2CVOPCV_RETURN_NAME_GV" set, then
               instead of returning a pointer to the subroutine it returns a
               pointer to the GV giving the most appropriate name for the
               subroutine in this context.  Normally this is just the "CvGV"
               of the subroutine, but for an anonymous ("CvANON") subroutine
               that is referenced through a GV it will be the referencing GV.
               The resulting "GV*" is cast to "CV*" to be returned.  A null
               pointer is returned as usual if there is no statically-
               determinable subroutine.

                       CV *    rv2cv_op_cv(OP *cvop, U32 flags)

Pack and Unpack
       packlist
               The engine implementing "pack()" Perl function.

                       void    packlist(SV *cat, const char *pat,
                                        const char *patend, SV **beglist,
                                        SV **endlist)

       unpackstring
               The engine implementing the "unpack()" Perl function.

               Using the template "pat..patend", this function unpacks the
               string "s..strend" into a number of mortal SVs, which it pushes
               onto the perl argument (@_) stack (so you will need to issue a
               "PUTBACK" before and "SPAGAIN" after the call to this
               function).  It returns the number of pushed elements.

               The "strend" and "patend" pointers should point to the byte
               following the last character of each string.

               Although this function returns its values on the perl argument
               stack, it doesn't take any parameters from that stack (and thus
               in particular there's no need to do a "PUSHMARK" before calling
               it, unlike "call_pv" for example).

                       SSize_t unpackstring(const char *pat,
                                            const char *patend, const char *s,
                                            const char *strend, U32 flags)

Pad Data Structures
       CvPADLIST
               NOTE: this function is experimental and may change or be
               removed without notice.

               CV's can have CvPADLIST(cv) set to point to a PADLIST.  This is
               the CV's scratchpad, which stores lexical variables and opcode
               temporary and per-thread values.

               For these purposes "formats" are a kind-of CV; eval""s are too
               (except they're not callable at will and are always thrown away
               after the eval"" is done executing).  Require'd files are
               simply evals without any outer lexical scope.

               XSUBs do not have a "CvPADLIST".  "dXSTARG" fetches values from
               "PL_curpad", but that is really the callers pad (a slot of
               which is allocated by every entersub). Do not get or set
               "CvPADLIST" if a CV is an XSUB (as determined by "CvISXSUB()"),
               "CvPADLIST" slot is reused for a different internal purpose in
               XSUBs.

               The PADLIST has a C array where pads are stored.

               The 0th entry of the PADLIST is a PADNAMELIST which represents
               the "names" or rather the "static type information" for
               lexicals.  The individual elements of a PADNAMELIST are
               PADNAMEs.  Future refactorings might stop the PADNAMELIST from
               being stored in the PADLIST's array, so don't rely on it.  See
               "PadlistNAMES".

               The CvDEPTH'th entry of a PADLIST is a PAD (an AV) which is the
               stack frame at that depth of recursion into the CV.  The 0th
               slot of a frame AV is an AV which is @_.  Other entries are
               storage for variables and op targets.

               Iterating over the PADNAMELIST iterates over all possible pad
               items.  Pad slots for targets ("SVs_PADTMP") and GVs end up
               having &PL_padname_undef "names", while slots for constants
               have &PL_padname_const "names" (see "pad_alloc").  That
               &PL_padname_undef and &PL_padname_const are used is an
               implementation detail subject to change.  To test for them, use
               "!PadnamePV(name)" and "PadnamePV(name)&&!PadnameLEN(name)",
               respectively.

               Only "my"/"our" variable slots get valid names.  The rest are
               op targets/GVs/constants which are statically allocated or
               resolved at compile time.  These don't have names by which they
               can be looked up from Perl code at run time through eval"" the
               way "my"/"our" variables can be.  Since they can't be looked up
               by "name" but only by their index allocated at compile time
               (which is usually in "PL_op->op_targ"), wasting a name SV for
               them doesn't make sense.

               The pad names in the PADNAMELIST have their PV holding the name
               of the variable.  The "COP_SEQ_RANGE_LOW" and "_HIGH" fields
               form a range (low+1..high inclusive) of cop_seq numbers for
               which the name is valid.  During compilation, these fields may
               hold the special value PERL_PADSEQ_INTRO to indicate various
               stages:

                COP_SEQ_RANGE_LOW        _HIGH
                -----------------        -----
                PERL_PADSEQ_INTRO            0   variable not yet introduced:
                                                 { my ($x
                valid-seq#   PERL_PADSEQ_INTRO   variable in scope:
                                                 { my ($x);
                valid-seq#          valid-seq#   compilation of scope complete:
                                                 { my ($x); .... }

               When a lexical var hasn't yet been introduced, it already
               exists from the perspective of duplicate declarations, but not
               for variable lookups, e.g.

                   my ($x, $x); # '"my" variable $x masks earlier declaration'
                   my $x = $x;  # equal to my $x = $::x;

               For typed lexicals "PadnameTYPE" points at the type stash.  For
               "our" lexicals, "PadnameOURSTASH" points at the stash of the
               associated global (so that duplicate "our" declarations in the
               same package can be detected).  "PadnameGEN" is sometimes used
               to store the generation number during compilation.

               If "PadnameOUTER" is set on the pad name, then that slot in the
               frame AV is a REFCNT'ed reference to a lexical from "outside".
               Such entries are sometimes referred to as 'fake'.  In this
               case, the name does not use 'low' and 'high' to store a cop_seq
               range, since it is in scope throughout.  Instead 'high' stores
               some flags containing info about the real lexical (is it
               declared in an anon, and is it capable of being instantiated
               multiple times?), and for fake ANONs, 'low' contains the index
               within the parent's pad where the lexical's value is stored, to
               make cloning quicker.

               If the 'name' is "&" the corresponding entry in the PAD is a CV
               representing a possible closure.

               Note that formats are treated as anon subs, and are cloned each
               time write is called (if necessary).

               The flag "SVs_PADSTALE" is cleared on lexicals each time the
               "my()" is executed, and set on scope exit.  This allows the
               "Variable $x is not available" warning to be generated in
               evals, such as

                   { my $x = 1; sub f { eval '$x'} } f();

               For state vars, "SVs_PADSTALE" is overloaded to mean 'not yet
               initialised', but this internal state is stored in a separate
               pad entry.

                       PADLIST * CvPADLIST(CV *cv)

       pad_add_name_pvs
               Exactly like "pad_add_name_pvn", but takes a literal string
               instead of a string/length pair.

                       PADOFFSET pad_add_name_pvs("literal string" name,
                                                  U32 flags, HV *typestash,
                                                  HV *ourstash)

       PadARRAY
               NOTE: this function is experimental and may change or be
               removed without notice.

               The C array of pad entries.

                       SV **   PadARRAY(PAD pad)

       pad_findmy_pvs
               Exactly like "pad_findmy_pvn", but takes a literal string
               instead of a string/length pair.

                       PADOFFSET pad_findmy_pvs("literal string" name,
                                                U32 flags)

       PadlistARRAY
               NOTE: this function is experimental and may change or be
               removed without notice.

               The C array of a padlist, containing the pads.  Only subscript
               it with numbers >= 1, as the 0th entry is not guaranteed to
               remain usable.

                       PAD **  PadlistARRAY(PADLIST padlist)

       PadlistMAX
               NOTE: this function is experimental and may change or be
               removed without notice.

               The index of the last allocated space in the padlist.  Note
               that the last pad may be in an earlier slot.  Any entries
               following it will be "NULL" in that case.

                       SSize_t PadlistMAX(PADLIST padlist)

       PadlistNAMES
               NOTE: this function is experimental and may change or be
               removed without notice.

               The names associated with pad entries.

                       PADNAMELIST * PadlistNAMES(PADLIST padlist)

       PadlistNAMESARRAY
               NOTE: this function is experimental and may change or be
               removed without notice.

               The C array of pad names.

                       PADNAME ** PadlistNAMESARRAY(PADLIST padlist)

       PadlistNAMESMAX
               NOTE: this function is experimental and may change or be
               removed without notice.

               The index of the last pad name.

                       SSize_t PadlistNAMESMAX(PADLIST padlist)

       PadlistREFCNT
               NOTE: this function is experimental and may change or be
               removed without notice.

               The reference count of the padlist.  Currently this is always
               1.

                       U32     PadlistREFCNT(PADLIST padlist)

       PadMAX  NOTE: this function is experimental and may change or be
               removed without notice.

               The index of the last pad entry.

                       SSize_t PadMAX(PAD pad)

       PadnameLEN
               NOTE: this function is experimental and may change or be
               removed without notice.

               The length of the name.

                       STRLEN  PadnameLEN(PADNAME pn)

       PadnamelistARRAY
               NOTE: this function is experimental and may change or be
               removed without notice.

               The C array of pad names.

                       PADNAME ** PadnamelistARRAY(PADNAMELIST pnl)

       PadnamelistMAX
               NOTE: this function is experimental and may change or be
               removed without notice.

               The index of the last pad name.

                       SSize_t PadnamelistMAX(PADNAMELIST pnl)

       PadnamelistREFCNT
               NOTE: this function is experimental and may change or be
               removed without notice.

               The reference count of the pad name list.

                       SSize_t PadnamelistREFCNT(PADNAMELIST pnl)

       PadnamelistREFCNT_dec
               NOTE: this function is experimental and may change or be
               removed without notice.

               Lowers the reference count of the pad name list.

                       void    PadnamelistREFCNT_dec(PADNAMELIST pnl)

       PadnamePV
               NOTE: this function is experimental and may change or be
               removed without notice.

               The name stored in the pad name struct.  This returns "NULL"
               for a target slot.

                       char *  PadnamePV(PADNAME pn)

       PadnameREFCNT
               NOTE: this function is experimental and may change or be
               removed without notice.

               The reference count of the pad name.

                       SSize_t PadnameREFCNT(PADNAME pn)

       PadnameREFCNT_dec
               NOTE: this function is experimental and may change or be
               removed without notice.

               Lowers the reference count of the pad name.

                       void    PadnameREFCNT_dec(PADNAME pn)

       PadnameSV
               NOTE: this function is experimental and may change or be
               removed without notice.

               Returns the pad name as a mortal SV.

                       SV *    PadnameSV(PADNAME pn)

       PadnameUTF8
               NOTE: this function is experimental and may change or be
               removed without notice.

               Whether PadnamePV is in UTF-8.  Currently, this is always true.

                       bool    PadnameUTF8(PADNAME pn)

       pad_new Create a new padlist, updating the global variables for the
               currently-compiling padlist to point to the new padlist.  The
               following flags can be OR'ed together:

                   padnew_CLONE        this pad is for a cloned CV
                   padnew_SAVE         save old globals on the save stack
                   padnew_SAVESUB      also save extra stuff for start of sub

                       PADLIST * pad_new(int flags)

       PL_comppad
               NOTE: this function is experimental and may change or be
               removed without notice.

               During compilation, this points to the array containing the
               values part of the pad for the currently-compiling code.  (At
               runtime a CV may have many such value arrays; at compile time
               just one is constructed.)  At runtime, this points to the array
               containing the currently-relevant values for the pad for the
               currently-executing code.

       PL_comppad_name
               NOTE: this function is experimental and may change or be
               removed without notice.

               During compilation, this points to the array containing the
               names part of the pad for the currently-compiling code.

       PL_curpad
               NOTE: this function is experimental and may change or be
               removed without notice.

               Points directly to the body of the "PL_comppad" array.  (I.e.,
               this is "PadARRAY(PL_comppad)".)

Per-Interpreter Variables
       PL_modglobal
               "PL_modglobal" is a general purpose, interpreter global HV for
               use by extensions that need to keep information on a per-
               interpreter basis.  In a pinch, it can also be used as a symbol
               table for extensions to share data among each other.  It is a
               good idea to use keys prefixed by the package name of the
               extension that owns the data.

                       HV*     PL_modglobal

       PL_na   A convenience variable which is typically used with "SvPV" when
               one doesn't care about the length of the string.  It is usually
               more efficient to either declare a local variable and use that
               instead or to use the "SvPV_nolen" macro.

                       STRLEN  PL_na

       PL_opfreehook
               When non-"NULL", the function pointed by this variable will be
               called each time an OP is freed with the corresponding OP as
               the argument.  This allows extensions to free any extra
               attribute they have locally attached to an OP.  It is also
               assured to first fire for the parent OP and then for its kids.

               When you replace this variable, it is considered a good
               practice to store the possibly previously installed hook and
               that you recall it inside your own.

                       Perl_ophook_t   PL_opfreehook

       PL_peepp
               Pointer to the per-subroutine peephole optimiser.  This is a
               function that gets called at the end of compilation of a Perl
               subroutine (or equivalently independent piece of Perl code) to
               perform fixups of some ops and to perform small-scale
               optimisations.  The function is called once for each subroutine
               that is compiled, and is passed, as sole parameter, a pointer
               to the op that is the entry point to the subroutine.  It
               modifies the op tree in place.

               The peephole optimiser should never be completely replaced.
               Rather, add code to it by wrapping the existing optimiser.  The
               basic way to do this can be seen in "Compile pass 3: peephole
               optimization" in perlguts.  If the new code wishes to operate
               on ops throughout the subroutine's structure, rather than just
               at the top level, it is likely to be more convenient to wrap
               the "PL_rpeepp" hook.

                       peep_t  PL_peepp

       PL_rpeepp
               Pointer to the recursive peephole optimiser.  This is a
               function that gets called at the end of compilation of a Perl
               subroutine (or equivalently independent piece of Perl code) to
               perform fixups of some ops and to perform small-scale
               optimisations.  The function is called once for each chain of
               ops linked through their "op_next" fields; it is recursively
               called to handle each side chain.  It is passed, as sole
               parameter, a pointer to the op that is at the head of the
               chain.  It modifies the op tree in place.

               The peephole optimiser should never be completely replaced.
               Rather, add code to it by wrapping the existing optimiser.  The
               basic way to do this can be seen in "Compile pass 3: peephole
               optimization" in perlguts.  If the new code wishes to operate
               only on ops at a subroutine's top level, rather than throughout
               the structure, it is likely to be more convenient to wrap the
               "PL_peepp" hook.

                       peep_t  PL_rpeepp

       PL_sv_no
               This is the "false" SV.  See "PL_sv_yes".  Always refer to this
               as &PL_sv_no.

                       SV      PL_sv_no

       PL_sv_undef
               This is the "undef" SV.  Always refer to this as &PL_sv_undef.

                       SV      PL_sv_undef

       PL_sv_yes
               This is the "true" SV.  See "PL_sv_no".  Always refer to this
               as &PL_sv_yes.

                       SV      PL_sv_yes

       PL_sv_zero
               This readonly SV has a zero numeric value and a "0" string
               value. It's similar to "PL_sv_no" except for its string value.
               Can be used as a cheap alternative to mXPUSHi(0) for example.
               Always refer to this as &PL_sv_zero. Introduced in 5.28.

                       SV      PL_sv_zero

REGEXP Functions
       SvRX    Convenience macro to get the REGEXP from a SV.  This is
               approximately equivalent to the following snippet:

                   if (SvMAGICAL(sv))
                       mg_get(sv);
                   if (SvROK(sv))
                       sv = MUTABLE_SV(SvRV(sv));
                   if (SvTYPE(sv) == SVt_REGEXP)
                       return (REGEXP*) sv;

               "NULL" will be returned if a REGEXP* is not found.

                       REGEXP * SvRX(SV *sv)

       SvRXOK  Returns a boolean indicating whether the SV (or the one it
               references) is a REGEXP.

               If you want to do something with the REGEXP* later use SvRX
               instead and check for NULL.

                       bool    SvRXOK(SV* sv)

Stack Manipulation Macros
       dMARK   Declare a stack marker variable, "mark", for the XSUB.  See
               "MARK" and "dORIGMARK".

                               dMARK;

       dORIGMARK
               Saves the original stack mark for the XSUB.  See "ORIGMARK".

                               dORIGMARK;

       dSP     Declares a local copy of perl's stack pointer for the XSUB,
               available via the "SP" macro.  See "SP".

                               dSP;

       EXTEND  Used to extend the argument stack for an XSUB's return values.
               Once used, guarantees that there is room for at least "nitems"
               to be pushed onto the stack.

                       void    EXTEND(SP, SSize_t nitems)

       MARK    Stack marker variable for the XSUB.  See "dMARK".

       mPUSHi  Push an integer onto the stack.  The stack must have room for
               this element.  Does not use "TARG".  See also "PUSHi",
               "mXPUSHi" and "XPUSHi".

                       void    mPUSHi(IV iv)

       mPUSHn  Push a double onto the stack.  The stack must have room for
               this element.  Does not use "TARG".  See also "PUSHn",
               "mXPUSHn" and "XPUSHn".

                       void    mPUSHn(NV nv)

       mPUSHp  Push a string onto the stack.  The stack must have room for
               this element.  The "len" indicates the length of the string.
               Does not use "TARG".  See also "PUSHp", "mXPUSHp" and "XPUSHp".

                       void    mPUSHp(char* str, STRLEN len)

       mPUSHs  Push an SV onto the stack and mortalizes the SV.  The stack
               must have room for this element.  Does not use "TARG".  See
               also "PUSHs" and "mXPUSHs".

                       void    mPUSHs(SV* sv)

       mPUSHu  Push an unsigned integer onto the stack.  The stack must have
               room for this element.  Does not use "TARG".  See also "PUSHu",
               "mXPUSHu" and "XPUSHu".

                       void    mPUSHu(UV uv)

       mXPUSHi Push an integer onto the stack, extending the stack if
               necessary.  Does not use "TARG".  See also "XPUSHi", "mPUSHi"
               and "PUSHi".

                       void    mXPUSHi(IV iv)

       mXPUSHn Push a double onto the stack, extending the stack if necessary.
               Does not use "TARG".  See also "XPUSHn", "mPUSHn" and "PUSHn".

                       void    mXPUSHn(NV nv)

       mXPUSHp Push a string onto the stack, extending the stack if necessary.
               The "len" indicates the length of the string.  Does not use
               "TARG".  See also "XPUSHp", "mPUSHp" and "PUSHp".

                       void    mXPUSHp(char* str, STRLEN len)

       mXPUSHs Push an SV onto the stack, extending the stack if necessary and
               mortalizes the SV.  Does not use "TARG".  See also "XPUSHs" and
               "mPUSHs".

                       void    mXPUSHs(SV* sv)

       mXPUSHu Push an unsigned integer onto the stack, extending the stack if
               necessary.  Does not use "TARG".  See also "XPUSHu", "mPUSHu"
               and "PUSHu".

                       void    mXPUSHu(UV uv)

       ORIGMARK
               The original stack mark for the XSUB.  See "dORIGMARK".

       POPi    Pops an integer off the stack.

                       IV      POPi

       POPl    Pops a long off the stack.

                       long    POPl

       POPn    Pops a double off the stack.

                       NV      POPn

       POPp    Pops a string off the stack.

                       char*   POPp

       POPpbytex
               Pops a string off the stack which must consist of bytes i.e.
               characters < 256.

                       char*   POPpbytex

       POPpx   Pops a string off the stack.  Identical to POPp.  There are two
               names for historical reasons.

                       char*   POPpx

       POPs    Pops an SV off the stack.

                       SV*     POPs

       POPu    Pops an unsigned integer off the stack.

                       UV      POPu

       POPul   Pops an unsigned long off the stack.

                       long    POPul

       PUSHi   Push an integer onto the stack.  The stack must have room for
               this element.  Handles 'set' magic.  Uses "TARG", so "dTARGET"
               or "dXSTARG" should be called to declare it.  Do not call
               multiple "TARG"-oriented macros to return lists from XSUB's -
               see "mPUSHi" instead.  See also "XPUSHi" and "mXPUSHi".

                       void    PUSHi(IV iv)

       PUSHMARK
               Opening bracket for arguments on a callback.  See "PUTBACK" and
               perlcall.

                       void    PUSHMARK(SP)

       PUSHmortal
               Push a new mortal SV onto the stack.  The stack must have room
               for this element.  Does not use "TARG".  See also "PUSHs",
               "XPUSHmortal" and "XPUSHs".

                       void    PUSHmortal()

       PUSHn   Push a double onto the stack.  The stack must have room for
               this element.  Handles 'set' magic.  Uses "TARG", so "dTARGET"
               or "dXSTARG" should be called to declare it.  Do not call
               multiple "TARG"-oriented macros to return lists from XSUB's -
               see "mPUSHn" instead.  See also "XPUSHn" and "mXPUSHn".

                       void    PUSHn(NV nv)

       PUSHp   Push a string onto the stack.  The stack must have room for
               this element.  The "len" indicates the length of the string.
               Handles 'set' magic.  Uses "TARG", so "dTARGET" or "dXSTARG"
               should be called to declare it.  Do not call multiple
               "TARG"-oriented macros to return lists from XSUB's - see
               "mPUSHp" instead.  See also "XPUSHp" and "mXPUSHp".

                       void    PUSHp(char* str, STRLEN len)

       PUSHs   Push an SV onto the stack.  The stack must have room for this
               element.  Does not handle 'set' magic.  Does not use "TARG".
               See also "PUSHmortal", "XPUSHs", and "XPUSHmortal".

                       void    PUSHs(SV* sv)

       PUSHu   Push an unsigned integer onto the stack.  The stack must have
               room for this element.  Handles 'set' magic.  Uses "TARG", so
               "dTARGET" or "dXSTARG" should be called to declare it.  Do not
               call multiple "TARG"-oriented macros to return lists from
               XSUB's - see "mPUSHu" instead.  See also "XPUSHu" and
               "mXPUSHu".

                       void    PUSHu(UV uv)

       PUTBACK Closing bracket for XSUB arguments.  This is usually handled by
               "xsubpp".  See "PUSHMARK" and perlcall for other uses.

                               PUTBACK;

       SP      Stack pointer.  This is usually handled by "xsubpp".  See "dSP"
               and "SPAGAIN".

       SPAGAIN Refetch the stack pointer.  Used after a callback.  See
               perlcall.

                               SPAGAIN;

       XPUSHi  Push an integer onto the stack, extending the stack if
               necessary.  Handles 'set' magic.  Uses "TARG", so "dTARGET" or
               "dXSTARG" should be called to declare it.  Do not call multiple
               "TARG"-oriented macros to return lists from XSUB's - see
               "mXPUSHi" instead.  See also "PUSHi" and "mPUSHi".

                       void    XPUSHi(IV iv)

       XPUSHmortal
               Push a new mortal SV onto the stack, extending the stack if
               necessary.  Does not use "TARG".  See also "XPUSHs",
               "PUSHmortal" and "PUSHs".

                       void    XPUSHmortal()

       XPUSHn  Push a double onto the stack, extending the stack if necessary.
               Handles 'set' magic.  Uses "TARG", so "dTARGET" or "dXSTARG"
               should be called to declare it.  Do not call multiple
               "TARG"-oriented macros to return lists from XSUB's - see
               "mXPUSHn" instead.  See also "PUSHn" and "mPUSHn".

                       void    XPUSHn(NV nv)

       XPUSHp  Push a string onto the stack, extending the stack if necessary.
               The "len" indicates the length of the string.  Handles 'set'
               magic.  Uses "TARG", so "dTARGET" or "dXSTARG" should be called
               to declare it.  Do not call multiple "TARG"-oriented macros to
               return lists from XSUB's - see "mXPUSHp" instead.  See also
               "PUSHp" and "mPUSHp".

                       void    XPUSHp(char* str, STRLEN len)

       XPUSHs  Push an SV onto the stack, extending the stack if necessary.
               Does not handle 'set' magic.  Does not use "TARG".  See also
               "XPUSHmortal", "PUSHs" and "PUSHmortal".

                       void    XPUSHs(SV* sv)

       XPUSHu  Push an unsigned integer onto the stack, extending the stack if
               necessary.  Handles 'set' magic.  Uses "TARG", so "dTARGET" or
               "dXSTARG" should be called to declare it.  Do not call multiple
               "TARG"-oriented macros to return lists from XSUB's - see
               "mXPUSHu" instead.  See also "PUSHu" and "mPUSHu".

                       void    XPUSHu(UV uv)

       XSRETURN
               Return from XSUB, indicating number of items on the stack.
               This is usually handled by "xsubpp".

                       void    XSRETURN(int nitems)

       XSRETURN_EMPTY
               Return an empty list from an XSUB immediately.

                               XSRETURN_EMPTY;

       XSRETURN_IV
               Return an integer from an XSUB immediately.  Uses "XST_mIV".

                       void    XSRETURN_IV(IV iv)

       XSRETURN_NO
               Return &PL_sv_no from an XSUB immediately.  Uses "XST_mNO".

                               XSRETURN_NO;

       XSRETURN_NV
               Return a double from an XSUB immediately.  Uses "XST_mNV".

                       void    XSRETURN_NV(NV nv)

       XSRETURN_PV
               Return a copy of a string from an XSUB immediately.  Uses
               "XST_mPV".

                       void    XSRETURN_PV(char* str)

       XSRETURN_UNDEF
               Return &PL_sv_undef from an XSUB immediately.  Uses
               "XST_mUNDEF".

                               XSRETURN_UNDEF;

       XSRETURN_UV
               Return an integer from an XSUB immediately.  Uses "XST_mUV".

                       void    XSRETURN_UV(IV uv)

       XSRETURN_YES
               Return &PL_sv_yes from an XSUB immediately.  Uses "XST_mYES".

                               XSRETURN_YES;

       XST_mIV Place an integer into the specified position "pos" on the
               stack.  The value is stored in a new mortal SV.

                       void    XST_mIV(int pos, IV iv)

       XST_mNO Place &PL_sv_no into the specified position "pos" on the stack.

                       void    XST_mNO(int pos)

       XST_mNV Place a double into the specified position "pos" on the stack.
               The value is stored in a new mortal SV.

                       void    XST_mNV(int pos, NV nv)

       XST_mPV Place a copy of a string into the specified position "pos" on
               the stack.  The value is stored in a new mortal SV.

                       void    XST_mPV(int pos, char* str)

       XST_mUNDEF
               Place &PL_sv_undef into the specified position "pos" on the
               stack.

                       void    XST_mUNDEF(int pos)

       XST_mYES
               Place &PL_sv_yes into the specified position "pos" on the
               stack.

                       void    XST_mYES(int pos)

SV Flags
       SVt_INVLIST
               Type flag for scalars.  See "svtype".

       SVt_IV  Type flag for scalars.  See "svtype".

       SVt_NULL
               Type flag for scalars.  See "svtype".

       SVt_NV  Type flag for scalars.  See "svtype".

       SVt_PV  Type flag for scalars.  See "svtype".

       SVt_PVAV
               Type flag for arrays.  See "svtype".

       SVt_PVCV
               Type flag for subroutines.  See "svtype".

       SVt_PVFM
               Type flag for formats.  See "svtype".

       SVt_PVGV
               Type flag for typeglobs.  See "svtype".

       SVt_PVHV
               Type flag for hashes.  See "svtype".

       SVt_PVIO
               Type flag for I/O objects.  See "svtype".

       SVt_PVIV
               Type flag for scalars.  See "svtype".

       SVt_PVLV
               Type flag for scalars.  See "svtype".

       SVt_PVMG
               Type flag for scalars.  See "svtype".

       SVt_PVNV
               Type flag for scalars.  See "svtype".

       SVt_REGEXP
               Type flag for regular expressions.  See "svtype".

       svtype  An enum of flags for Perl types.  These are found in the file
               sv.h in the "svtype" enum.  Test these flags with the "SvTYPE"
               macro.

               The types are:

                   SVt_NULL
                   SVt_IV
                   SVt_NV
                   SVt_RV
                   SVt_PV
                   SVt_PVIV
                   SVt_PVNV
                   SVt_PVMG
                   SVt_INVLIST
                   SVt_REGEXP
                   SVt_PVGV
                   SVt_PVLV
                   SVt_PVAV
                   SVt_PVHV
                   SVt_PVCV
                   SVt_PVFM
                   SVt_PVIO

               These are most easily explained from the bottom up.

               "SVt_PVIO" is for I/O objects, "SVt_PVFM" for formats,
               "SVt_PVCV" for subroutines, "SVt_PVHV" for hashes and
               "SVt_PVAV" for arrays.

               All the others are scalar types, that is, things that can be
               bound to a "$" variable.  For these, the internal types are
               mostly orthogonal to types in the Perl language.

               Hence, checking "SvTYPE(sv) < SVt_PVAV" is the best way to see
               whether something is a scalar.

               "SVt_PVGV" represents a typeglob.  If "!SvFAKE(sv)", then it is
               a real, incoercible typeglob.  If "SvFAKE(sv)", then it is a
               scalar to which a typeglob has been assigned.  Assigning to it
               again will stop it from being a typeglob.  "SVt_PVLV"
               represents a scalar that delegates to another scalar behind the
               scenes.  It is used, e.g., for the return value of "substr" and
               for tied hash and array elements.  It can hold any scalar
               value, including a typeglob.  "SVt_REGEXP" is for regular
               expressions.  "SVt_INVLIST" is for Perl core internal use only.

               "SVt_PVMG" represents a "normal" scalar (not a typeglob,
               regular expression, or delegate).  Since most scalars do not
               need all the internal fields of a PVMG, we save memory by
               allocating smaller structs when possible.  All the other types
               are just simpler forms of "SVt_PVMG", with fewer internal
               fields.  "SVt_NULL" can only hold undef.  "SVt_IV" can hold
               undef, an integer, or a reference.  ("SVt_RV" is an alias for
               "SVt_IV", which exists for backward compatibility.)  "SVt_NV"
               can hold any of those or a double.  "SVt_PV" can only hold
               "undef" or a string.  "SVt_PVIV" is a superset of "SVt_PV" and
               "SVt_IV".  "SVt_PVNV" is similar.  "SVt_PVMG" can hold anything
               "SVt_PVNV" can hold, but it can, but does not have to, be
               blessed or magical.

SV Manipulation Functions
       boolSV  Returns a true SV if "b" is a true value, or a false SV if "b"
               is 0.

               See also "PL_sv_yes" and "PL_sv_no".

                       SV *    boolSV(bool b)

       croak_xs_usage
               A specialised variant of "croak()" for emitting the usage
               message for xsubs

                   croak_xs_usage(cv, "eee_yow");

               works out the package name and subroutine name from "cv", and
               then calls "croak()".  Hence if "cv" is &ouch::awk, it would
               call "croak" as:

                Perl_croak(aTHX_ "Usage: %" SVf "::%" SVf "(%s)", "ouch" "awk",
                                                                    "eee_yow");

                       void    croak_xs_usage(const CV *const cv,
                                              const char *const params)

       get_sv  Returns the SV of the specified Perl scalar.  "flags" are
               passed to "gv_fetchpv".  If "GV_ADD" is set and the Perl
               variable does not exist then it will be created.  If "flags" is
               zero and the variable does not exist then NULL is returned.

               NOTE: the perl_ form of this function is deprecated.

                       SV*     get_sv(const char *name, I32 flags)

       looks_like_number
               Test if the content of an SV looks like a number (or is a
               number).  "Inf" and "Infinity" are treated as numbers (so will
               not issue a non-numeric warning), even if your "atof()" doesn't
               grok them.  Get-magic is ignored.

                       I32     looks_like_number(SV *const sv)

       newRV_inc
               Creates an RV wrapper for an SV.  The reference count for the
               original SV is incremented.

                       SV*     newRV_inc(SV* sv)

       newRV_noinc
               Creates an RV wrapper for an SV.  The reference count for the
               original SV is not incremented.

                       SV*     newRV_noinc(SV *const tmpRef)

       newSV   Creates a new SV.  A non-zero "len" parameter indicates the
               number of bytes of preallocated string space the SV should
               have.  An extra byte for a trailing "NUL" is also reserved.
               ("SvPOK" is not set for the SV even if string space is
               allocated.)  The reference count for the new SV is set to 1.

               In 5.9.3, "newSV()" replaces the older "NEWSV()" API, and drops
               the first parameter, x, a debug aid which allowed callers to
               identify themselves.  This aid has been superseded by a new
               build option, "PERL_MEM_LOG" (see "PERL_MEM_LOG" in
               perlhacktips).  The older API is still there for use in XS
               modules supporting older perls.

                       SV*     newSV(const STRLEN len)

       newSVhek
               Creates a new SV from the hash key structure.  It will generate
               scalars that point to the shared string table where possible.
               Returns a new (undefined) SV if "hek" is NULL.

                       SV*     newSVhek(const HEK *const hek)

       newSViv Creates a new SV and copies an integer into it.  The reference
               count for the SV is set to 1.

                       SV*     newSViv(const IV i)

       newSVnv Creates a new SV and copies a floating point value into it.
               The reference count for the SV is set to 1.

                       SV*     newSVnv(const NV n)

       newSVpadname
               NOTE: this function is experimental and may change or be
               removed without notice.

               Creates a new SV containing the pad name.

                       SV*     newSVpadname(PADNAME *pn)

       newSVpv Creates a new SV and copies a string (which may contain "NUL"
               ("\0") characters) into it.  The reference count for the SV is
               set to 1.  If "len" is zero, Perl will compute the length using
               "strlen()", (which means if you use this option, that "s" can't
               have embedded "NUL" characters and has to have a terminating
               "NUL" byte).

               This function can cause reliability issues if you are likely to
               pass in empty strings that are not null terminated, because it
               will run strlen on the string and potentially run past valid
               memory.

               Using "newSVpvn" is a safer alternative for non "NUL"
               terminated strings.  For string literals use "newSVpvs"
               instead.  This function will work fine for "NUL" terminated
               strings, but if you want to avoid the if statement on whether
               to call "strlen" use "newSVpvn" instead (calling "strlen"
               yourself).

                       SV*     newSVpv(const char *const s, const STRLEN len)

       newSVpvf
               Creates a new SV and initializes it with the string formatted
               like "sv_catpvf".

                       SV*     newSVpvf(const char *const pat, ...)

       newSVpvn
               Creates a new SV and copies a string into it, which may contain
               "NUL" characters ("\0") and other binary data.  The reference
               count for the SV is set to 1.  Note that if "len" is zero, Perl
               will create a zero length (Perl) string.  You are responsible
               for ensuring that the source buffer is at least "len" bytes
               long.  If the "buffer" argument is NULL the new SV will be
               undefined.

                       SV*     newSVpvn(const char *const buffer,
                                        const STRLEN len)

       newSVpvn_flags
               Creates a new SV and copies a string (which may contain "NUL"
               ("\0") characters) into it.  The reference count for the SV is
               set to 1.  Note that if "len" is zero, Perl will create a zero
               length string.  You are responsible for ensuring that the
               source string is at least "len" bytes long.  If the "s"
               argument is NULL the new SV will be undefined.  Currently the
               only flag bits accepted are "SVf_UTF8" and "SVs_TEMP".  If
               "SVs_TEMP" is set, then "sv_2mortal()" is called on the result
               before returning.  If "SVf_UTF8" is set, "s" is considered to
               be in UTF-8 and the "SVf_UTF8" flag will be set on the new SV.
               "newSVpvn_utf8()" is a convenience wrapper for this function,
               defined as

                   #define newSVpvn_utf8(s, len, u)                    \
                       newSVpvn_flags((s), (len), (u) ? SVf_UTF8 : 0)

                       SV*     newSVpvn_flags(const char *const s,
                                              const STRLEN len,
                                              const U32 flags)

       newSVpvn_share
               Creates a new SV with its "SvPVX_const" pointing to a shared
               string in the string table.  If the string does not already
               exist in the table, it is created first.  Turns on the
               "SvIsCOW" flag (or "READONLY" and "FAKE" in 5.16 and earlier).
               If the "hash" parameter is non-zero, that value is used;
               otherwise the hash is computed.  The string's hash can later be
               retrieved from the SV with the "SvSHARED_HASH()" macro.  The
               idea here is that as the string table is used for shared hash
               keys these strings will have "SvPVX_const == HeKEY" and hash
               lookup will avoid string compare.

                       SV*     newSVpvn_share(const char* s, I32 len, U32 hash)

       newSVpvn_utf8
               Creates a new SV and copies a string (which may contain "NUL"
               ("\0") characters) into it.  If "utf8" is true, calls
               "SvUTF8_on" on the new SV.  Implemented as a wrapper around
               "newSVpvn_flags".

                       SV*     newSVpvn_utf8(const char* s, STRLEN len,
                                             U32 utf8)

       newSVpvs
               Like "newSVpvn", but takes a literal string instead of a
               string/length pair.

                       SV*     newSVpvs("literal string" s)

       newSVpvs_flags
               Like "newSVpvn_flags", but takes a literal string instead of a
               string/length pair.

                       SV*     newSVpvs_flags("literal string" s, U32 flags)

       newSVpv_share
               Like "newSVpvn_share", but takes a "NUL"-terminated string
               instead of a string/length pair.

                       SV*     newSVpv_share(const char* s, U32 hash)

       newSVpvs_share
               Like "newSVpvn_share", but takes a literal string instead of a
               string/length pair and omits the hash parameter.

                       SV*     newSVpvs_share("literal string" s)

       newSVrv Creates a new SV for the existing RV, "rv", to point to.  If
               "rv" is not an RV then it will be upgraded to one.  If
               "classname" is non-null then the new SV will be blessed in the
               specified package.  The new SV is returned and its reference
               count is 1.  The reference count 1 is owned by "rv". See also
               newRV_inc() and newRV_noinc() for creating a new RV properly.

                       SV*     newSVrv(SV *const rv,
                                       const char *const classname)

       newSVsv Creates a new SV which is an exact duplicate of the original
               SV.  (Uses "sv_setsv".)

                       SV*     newSVsv(SV *const old)

       newSVsv_nomg
               Like "newSVsv" but does not process get magic.

                       SV*     newSVsv_nomg(SV *const old)

       newSV_type
               Creates a new SV, of the type specified.  The reference count
               for the new SV is set to 1.

                       SV*     newSV_type(const svtype type)

       newSVuv Creates a new SV and copies an unsigned integer into it.  The
               reference count for the SV is set to 1.

                       SV*     newSVuv(const UV u)

       sv_2bool
               This macro is only used by "sv_true()" or its macro equivalent,
               and only if the latter's argument is neither "SvPOK", "SvIOK"
               nor "SvNOK".  It calls "sv_2bool_flags" with the "SV_GMAGIC"
               flag.

                       bool    sv_2bool(SV *const sv)

       sv_2bool_flags
               This function is only used by "sv_true()" and friends,  and
               only if the latter's argument is neither "SvPOK", "SvIOK" nor
               "SvNOK".  If the flags contain "SV_GMAGIC", then it does an
               "mg_get()" first.

                       bool    sv_2bool_flags(SV *sv, I32 flags)

       sv_2cv  Using various gambits, try to get a CV from an SV; in addition,
               try if possible to set *st and *gvp to the stash and GV
               associated with it.  The flags in "lref" are passed to
               "gv_fetchsv".

                       CV*     sv_2cv(SV* sv, HV **const st, GV **const gvp,
                                      const I32 lref)

       sv_2io  Using various gambits, try to get an IO from an SV: the IO slot
               if its a GV; or the recursive result if we're an RV; or the IO
               slot of the symbol named after the PV if we're a string.

               'Get' magic is ignored on the "sv" passed in, but will be
               called on "SvRV(sv)" if "sv" is an RV.

                       IO*     sv_2io(SV *const sv)

       sv_2iv_flags
               Return the integer value of an SV, doing any necessary string
               conversion.  If "flags" has the "SV_GMAGIC" bit set, does an
               "mg_get()" first.  Normally used via the "SvIV(sv)" and
               "SvIVx(sv)" macros.

                       IV      sv_2iv_flags(SV *const sv, const I32 flags)

       sv_2mortal
               Marks an existing SV as mortal.  The SV will be destroyed
               "soon", either by an explicit call to "FREETMPS", or by an
               implicit call at places such as statement boundaries.
               "SvTEMP()" is turned on which means that the SV's string buffer
               can be "stolen" if this SV is copied.  See also "sv_newmortal"
               and "sv_mortalcopy".

                       SV*     sv_2mortal(SV *const sv)

       sv_2nv_flags
               Return the num value of an SV, doing any necessary string or
               integer conversion.  If "flags" has the "SV_GMAGIC" bit set,
               does an "mg_get()" first.  Normally used via the "SvNV(sv)" and
               "SvNVx(sv)" macros.

                       NV      sv_2nv_flags(SV *const sv, const I32 flags)

       sv_2pvbyte
               Return a pointer to the byte-encoded representation of the SV,
               and set *lp to its length.  May cause the SV to be downgraded
               from UTF-8 as a side-effect.

               Usually accessed via the "SvPVbyte" macro.

                       char*   sv_2pvbyte(SV *sv, STRLEN *const lp)

       sv_2pvutf8
               Return a pointer to the UTF-8-encoded representation of the SV,
               and set *lp to its length.  May cause the SV to be upgraded to
               UTF-8 as a side-effect.

               Usually accessed via the "SvPVutf8" macro.

                       char*   sv_2pvutf8(SV *sv, STRLEN *const lp)

       sv_2pv_flags
               Returns a pointer to the string value of an SV, and sets *lp to
               its length.  If flags has the "SV_GMAGIC" bit set, does an
               "mg_get()" first.  Coerces "sv" to a string if necessary.
               Normally invoked via the "SvPV_flags" macro.  "sv_2pv()" and
               "sv_2pv_nomg" usually end up here too.

                       char*   sv_2pv_flags(SV *const sv, STRLEN *const lp,
                                            const I32 flags)

       sv_2uv_flags
               Return the unsigned integer value of an SV, doing any necessary
               string conversion.  If "flags" has the "SV_GMAGIC" bit set,
               does an "mg_get()" first.  Normally used via the "SvUV(sv)" and
               "SvUVx(sv)" macros.

                       UV      sv_2uv_flags(SV *const sv, const I32 flags)

       sv_backoff
               Remove any string offset.  You should normally use the
               "SvOOK_off" macro wrapper instead.

                       void    sv_backoff(SV *const sv)

       sv_bless
               Blesses an SV into a specified package.  The SV must be an RV.
               The package must be designated by its stash (see "gv_stashpv").
               The reference count of the SV is unaffected.

                       SV*     sv_bless(SV *const sv, HV *const stash)

       sv_catpv
               Concatenates the "NUL"-terminated string onto the end of the
               string which is in the SV.  If the SV has the UTF-8 status set,
               then the bytes appended should be valid UTF-8.  Handles 'get'
               magic, but not 'set' magic.  See "sv_catpv_mg".

                       void    sv_catpv(SV *const sv, const char* ptr)

       sv_catpvf
               Processes its arguments like "sprintf", and appends the
               formatted output to an SV.  As with "sv_vcatpvfn" called with a
               non-null C-style variable argument list, argument reordering is
               not supported.  If the appended data contains "wide" characters
               (including, but not limited to, SVs with a UTF-8 PV formatted
               with %s, and characters >255 formatted with %c), the original
               SV might get upgraded to UTF-8.  Handles 'get' magic, but not
               'set' magic.  See "sv_catpvf_mg".  If the original SV was
               UTF-8, the pattern should be valid UTF-8; if the original SV
               was bytes, the pattern should be too.

                       void    sv_catpvf(SV *const sv, const char *const pat,
                                         ...)

       sv_catpvf_mg
               Like "sv_catpvf", but also handles 'set' magic.

                       void    sv_catpvf_mg(SV *const sv,
                                            const char *const pat, ...)

       sv_catpvn
               Concatenates the string onto the end of the string which is in
               the SV.  "len" indicates number of bytes to copy.  If the SV
               has the UTF-8 status set, then the bytes appended should be
               valid UTF-8.  Handles 'get' magic, but not 'set' magic.  See
               "sv_catpvn_mg".

                       void    sv_catpvn(SV *dsv, const char *sstr, STRLEN len)

       sv_catpvn_flags
               Concatenates the string onto the end of the string which is in
               the SV.  The "len" indicates number of bytes to copy.

               By default, the string appended is assumed to be valid UTF-8 if
               the SV has the UTF-8 status set, and a string of bytes
               otherwise.  One can force the appended string to be interpreted
               as UTF-8 by supplying the "SV_CATUTF8" flag, and as bytes by
               supplying the "SV_CATBYTES" flag; the SV or the string appended
               will be upgraded to UTF-8 if necessary.

               If "flags" has the "SV_SMAGIC" bit set, will "mg_set" on "dsv"
               afterwards if appropriate.  "sv_catpvn" and "sv_catpvn_nomg"
               are implemented in terms of this function.

                       void    sv_catpvn_flags(SV *const dstr,
                                               const char *sstr,
                                               const STRLEN len,
                                               const I32 flags)

       sv_catpvn_nomg
               Like "sv_catpvn" but doesn't process magic.

                       void    sv_catpvn_nomg(SV* sv, const char* ptr,
                                              STRLEN len)

       sv_catpvs
               Like "sv_catpvn", but takes a literal string instead of a
               string/length pair.

                       void    sv_catpvs(SV* sv, "literal string" s)

       sv_catpvs_flags
               Like "sv_catpvn_flags", but takes a literal string instead of a
               string/length pair.

                       void    sv_catpvs_flags(SV* sv, "literal string" s,
                                               I32 flags)

       sv_catpvs_mg
               Like "sv_catpvn_mg", but takes a literal string instead of a
               string/length pair.

                       void    sv_catpvs_mg(SV* sv, "literal string" s)

       sv_catpvs_nomg
               Like "sv_catpvn_nomg", but takes a literal string instead of a
               string/length pair.

                       void    sv_catpvs_nomg(SV* sv, "literal string" s)

       sv_catpv_flags
               Concatenates the "NUL"-terminated string onto the end of the
               string which is in the SV.  If the SV has the UTF-8 status set,
               then the bytes appended should be valid UTF-8.  If "flags" has
               the "SV_SMAGIC" bit set, will "mg_set" on the modified SV if
               appropriate.

                       void    sv_catpv_flags(SV *dstr, const char *sstr,
                                              const I32 flags)

       sv_catpv_mg
               Like "sv_catpv", but also handles 'set' magic.

                       void    sv_catpv_mg(SV *const sv, const char *const ptr)

       sv_catpv_nomg
               Like "sv_catpv" but doesn't process magic.

                       void    sv_catpv_nomg(SV* sv, const char* ptr)

       sv_catsv
               Concatenates the string from SV "ssv" onto the end of the
               string in SV "dsv".  If "ssv" is null, does nothing; otherwise
               modifies only "dsv".  Handles 'get' magic on both SVs, but no
               'set' magic.  See "sv_catsv_mg" and "sv_catsv_nomg".

                       void    sv_catsv(SV *dstr, SV *sstr)

       sv_catsv_flags
               Concatenates the string from SV "ssv" onto the end of the
               string in SV "dsv".  If "ssv" is null, does nothing; otherwise
               modifies only "dsv".  If "flags" has the "SV_GMAGIC" bit set,
               will call "mg_get" on both SVs if appropriate.  If "flags" has
               the "SV_SMAGIC" bit set, "mg_set" will be called on the
               modified SV afterward, if appropriate.  "sv_catsv",
               "sv_catsv_nomg", and "sv_catsv_mg" are implemented in terms of
               this function.

                       void    sv_catsv_flags(SV *const dsv, SV *const ssv,
                                              const I32 flags)

       sv_catsv_nomg
               Like "sv_catsv" but doesn't process magic.

                       void    sv_catsv_nomg(SV* dsv, SV* ssv)

       sv_chop Efficient removal of characters from the beginning of the
               string buffer.  "SvPOK(sv)", or at least "SvPOKp(sv)", must be
               true and "ptr" must be a pointer to somewhere inside the string
               buffer.  "ptr" becomes the first character of the adjusted
               string.  Uses the "OOK" hack.  On return, only "SvPOK(sv)" and
               "SvPOKp(sv)" among the "OK" flags will be true.

               Beware: after this function returns, "ptr" and SvPVX_const(sv)
               may no longer refer to the same chunk of data.

               The unfortunate similarity of this function's name to that of
               Perl's "chop" operator is strictly coincidental.  This function
               works from the left; "chop" works from the right.

                       void    sv_chop(SV *const sv, const char *const ptr)

       sv_clear
               Clear an SV: call any destructors, free up any memory used by
               the body, and free the body itself.  The SV's head is not
               freed, although its type is set to all 1's so that it won't
               inadvertently be assumed to be live during global destruction
               etc.  This function should only be called when "REFCNT" is
               zero.  Most of the time you'll want to call "sv_free()" (or its
               macro wrapper "SvREFCNT_dec") instead.

                       void    sv_clear(SV *const orig_sv)

       sv_cmp  Compares the strings in two SVs.  Returns -1, 0, or 1
               indicating whether the string in "sv1" is less than, equal to,
               or greater than the string in "sv2".  Is UTF-8 and 'usebytes'
               aware, handles get magic, and will coerce its args to strings
               if necessary.  See also "sv_cmp_locale".

                       I32     sv_cmp(SV *const sv1, SV *const sv2)

       sv_cmp_flags
               Compares the strings in two SVs.  Returns -1, 0, or 1
               indicating whether the string in "sv1" is less than, equal to,
               or greater than the string in "sv2".  Is UTF-8 and 'usebytes'
               aware and will coerce its args to strings if necessary.  If the
               flags has the "SV_GMAGIC" bit set, it handles get magic.  See
               also "sv_cmp_locale_flags".

                       I32     sv_cmp_flags(SV *const sv1, SV *const sv2,
                                            const U32 flags)

       sv_cmp_locale
               Compares the strings in two SVs in a locale-aware manner.  Is
               UTF-8 and 'usebytes' aware, handles get magic, and will coerce
               its args to strings if necessary.  See also "sv_cmp".

                       I32     sv_cmp_locale(SV *const sv1, SV *const sv2)

       sv_cmp_locale_flags
               Compares the strings in two SVs in a locale-aware manner.  Is
               UTF-8 and 'usebytes' aware and will coerce its args to strings
               if necessary.  If the flags contain "SV_GMAGIC", it handles get
               magic.  See also "sv_cmp_flags".

                       I32     sv_cmp_locale_flags(SV *const sv1,
                                                   SV *const sv2,
                                                   const U32 flags)

       sv_collxfrm
               This calls "sv_collxfrm_flags" with the SV_GMAGIC flag.  See
               "sv_collxfrm_flags".

                       char*   sv_collxfrm(SV *const sv, STRLEN *const nxp)

       sv_collxfrm_flags
               Add Collate Transform magic to an SV if it doesn't already have
               it.  If the flags contain "SV_GMAGIC", it handles get-magic.

               Any scalar variable may carry "PERL_MAGIC_collxfrm" magic that
               contains the scalar data of the variable, but transformed to
               such a format that a normal memory comparison can be used to
               compare the data according to the locale settings.

                       char*   sv_collxfrm_flags(SV *const sv,
                                                 STRLEN *const nxp,
                                                 I32 const flags)

       sv_copypv
               Copies a stringified representation of the source SV into the
               destination SV.  Automatically performs any necessary "mg_get"
               and coercion of numeric values into strings.  Guaranteed to
               preserve "UTF8" flag even from overloaded objects.  Similar in
               nature to "sv_2pv[_flags]" but operates directly on an SV
               instead of just the string.  Mostly uses "sv_2pv_flags" to do
               its work, except when that would lose the UTF-8'ness of the PV.

                       void    sv_copypv(SV *const dsv, SV *const ssv)

       sv_copypv_flags
               Implementation of "sv_copypv" and "sv_copypv_nomg".  Calls get
               magic iff flags has the "SV_GMAGIC" bit set.

                       void    sv_copypv_flags(SV *const dsv, SV *const ssv,
                                               const I32 flags)

       sv_copypv_nomg
               Like "sv_copypv", but doesn't invoke get magic first.

                       void    sv_copypv_nomg(SV *const dsv, SV *const ssv)

       SvCUR   Returns the length of the string which is in the SV.  See
               "SvLEN".

                       STRLEN  SvCUR(SV* sv)

       SvCUR_set
               Set the current length of the string which is in the SV.  See
               "SvCUR" and "SvIV_set">.

                       void    SvCUR_set(SV* sv, STRLEN len)

       sv_dec  Auto-decrement of the value in the SV, doing string to numeric
               conversion if necessary.  Handles 'get' magic and operator
               overloading.

                       void    sv_dec(SV *const sv)

       sv_dec_nomg
               Auto-decrement of the value in the SV, doing string to numeric
               conversion if necessary.  Handles operator overloading.  Skips
               handling 'get' magic.

                       void    sv_dec_nomg(SV *const sv)

       sv_derived_from
               Exactly like "sv_derived_from_pv", but doesn't take a "flags"
               parameter.

                       bool    sv_derived_from(SV* sv, const char *const name)

       sv_derived_from_pv
               Exactly like "sv_derived_from_pvn", but takes a nul-terminated
               string instead of a string/length pair.

                       bool    sv_derived_from_pv(SV* sv,
                                                  const char *const name,
                                                  U32 flags)

       sv_derived_from_pvn
               Returns a boolean indicating whether the SV is derived from the
               specified class at the C level.  To check derivation at the
               Perl level, call "isa()" as a normal Perl method.

               Currently, the only significant value for "flags" is SVf_UTF8.

                       bool    sv_derived_from_pvn(SV* sv,
                                                   const char *const name,
                                                   const STRLEN len, U32 flags)

       sv_derived_from_sv
               Exactly like "sv_derived_from_pvn", but takes the name string
               in the form of an SV instead of a string/length pair.

                       bool    sv_derived_from_sv(SV* sv, SV *namesv,
                                                  U32 flags)

       sv_does Like "sv_does_pv", but doesn't take a "flags" parameter.

                       bool    sv_does(SV* sv, const char *const name)

       sv_does_pv
               Like "sv_does_sv", but takes a nul-terminated string instead of
               an SV.

                       bool    sv_does_pv(SV* sv, const char *const name,
                                          U32 flags)

       sv_does_pvn
               Like "sv_does_sv", but takes a string/length pair instead of an
               SV.

                       bool    sv_does_pvn(SV* sv, const char *const name,
                                           const STRLEN len, U32 flags)

       sv_does_sv
               Returns a boolean indicating whether the SV performs a
               specific, named role.  The SV can be a Perl object or the name
               of a Perl class.

                       bool    sv_does_sv(SV* sv, SV* namesv, U32 flags)

       SvEND   Returns a pointer to the spot just after the last character in
               the string which is in the SV, where there is usually a
               trailing "NUL" character (even though Perl scalars do not
               strictly require it).  See "SvCUR".  Access the character as
               "*(SvEND(sv))".

               Warning: If "SvCUR" is equal to "SvLEN", then "SvEND" points to
               unallocated memory.

                       char*   SvEND(SV* sv)

       sv_eq   Returns a boolean indicating whether the strings in the two SVs
               are identical.  Is UTF-8 and 'usebytes' aware, handles get
               magic, and will coerce its args to strings if necessary.

                       I32     sv_eq(SV* sv1, SV* sv2)

       sv_eq_flags
               Returns a boolean indicating whether the strings in the two SVs
               are identical.  Is UTF-8 and 'usebytes' aware and coerces its
               args to strings if necessary.  If the flags has the "SV_GMAGIC"
               bit set, it handles get-magic, too.

                       I32     sv_eq_flags(SV* sv1, SV* sv2, const U32 flags)

       sv_force_normal_flags
               Undo various types of fakery on an SV, where fakery means "more
               than" a string: if the PV is a shared string, make a private
               copy; if we're a ref, stop refing; if we're a glob, downgrade
               to an "xpvmg"; if we're a copy-on-write scalar, this is the on-
               write time when we do the copy, and is also used locally; if
               this is a vstring, drop the vstring magic.  If "SV_COW_DROP_PV"
               is set then a copy-on-write scalar drops its PV buffer (if any)
               and becomes "SvPOK_off" rather than making a copy.  (Used where
               this scalar is about to be set to some other value.)  In
               addition, the "flags" parameter gets passed to
               "sv_unref_flags()" when unreffing.  "sv_force_normal" calls
               this function with flags set to 0.

               This function is expected to be used to signal to perl that
               this SV is about to be written to, and any extra book-keeping
               needs to be taken care of.  Hence, it croaks on read-only
               values.

                       void    sv_force_normal_flags(SV *const sv,
                                                     const U32 flags)

       sv_free Decrement an SV's reference count, and if it drops to zero,
               call "sv_clear" to invoke destructors and free up any memory
               used by the body; finally, deallocating the SV's head itself.
               Normally called via a wrapper macro "SvREFCNT_dec".

                       void    sv_free(SV *const sv)

       SvGAMAGIC
               Returns true if the SV has get magic or overloading.  If either
               is true then the scalar is active data, and has the potential
               to return a new value every time it is accessed.  Hence you
               must be careful to only read it once per user logical operation
               and work with that returned value.  If neither is true then the
               scalar's value cannot change unless written to.

                       U32     SvGAMAGIC(SV* sv)

       sv_gets Get a line from the filehandle and store it into the SV,
               optionally appending to the currently-stored string.  If
               "append" is not 0, the line is appended to the SV instead of
               overwriting it.  "append" should be set to the byte offset that
               the appended string should start at in the SV (typically,
               "SvCUR(sv)" is a suitable choice).

                       char*   sv_gets(SV *const sv, PerlIO *const fp,
                                       I32 append)

       sv_get_backrefs
               NOTE: this function is experimental and may change or be
               removed without notice.

               If "sv" is the target of a weak reference then it returns the
               back references structure associated with the sv; otherwise
               return "NULL".

               When returning a non-null result the type of the return is
               relevant. If it is an AV then the elements of the AV are the
               weak reference RVs which point at this item. If it is any other
               type then the item itself is the weak reference.

               See also "Perl_sv_add_backref()", "Perl_sv_del_backref()",
               "Perl_sv_kill_backrefs()"

                       SV*     sv_get_backrefs(SV *const sv)

       SvGROW  Expands the character buffer in the SV so that it has room for
               the indicated number of bytes (remember to reserve space for an
               extra trailing "NUL" character).  Calls "sv_grow" to perform
               the expansion if necessary.  Returns a pointer to the character
               buffer.  SV must be of type >= "SVt_PV".  One alternative is to
               call "sv_grow" if you are not sure of the type of SV.

               You might mistakenly think that "len" is the number of bytes to
               add to the existing size, but instead it is the total size "sv"
               should be.

                       char *  SvGROW(SV* sv, STRLEN len)

       sv_grow Expands the character buffer in the SV.  If necessary, uses
               "sv_unref" and upgrades the SV to "SVt_PV".  Returns a pointer
               to the character buffer.  Use the "SvGROW" wrapper instead.

                       char*   sv_grow(SV *const sv, STRLEN newlen)

       sv_inc  Auto-increment of the value in the SV, doing string to numeric
               conversion if necessary.  Handles 'get' magic and operator
               overloading.

                       void    sv_inc(SV *const sv)

       sv_inc_nomg
               Auto-increment of the value in the SV, doing string to numeric
               conversion if necessary.  Handles operator overloading.  Skips
               handling 'get' magic.

                       void    sv_inc_nomg(SV *const sv)

       sv_insert
               Inserts and/or replaces a string at the specified offset/length
               within the SV.  Similar to the Perl "substr()" function, with
               "littlelen" bytes starting at "little" replacing "len" bytes of
               the string in "bigstr" starting at "offset".  Handles get
               magic.

                       void    sv_insert(SV *const bigstr, const STRLEN offset,
                                         const STRLEN len,
                                         const char *const little,
                                         const STRLEN littlelen)

       sv_insert_flags
               Same as "sv_insert", but the extra "flags" are passed to the
               "SvPV_force_flags" that applies to "bigstr".

                       void    sv_insert_flags(SV *const bigstr,
                                               const STRLEN offset,
                                               const STRLEN len,
                                               const char *little,
                                               const STRLEN littlelen,
                                               const U32 flags)

       SvIOK   Returns a U32 value indicating whether the SV contains an
               integer.

                       U32     SvIOK(SV* sv)

       SvIOK_notUV
               Returns a boolean indicating whether the SV contains a signed
               integer.

                       bool    SvIOK_notUV(SV* sv)

       SvIOK_off
               Unsets the IV status of an SV.

                       void    SvIOK_off(SV* sv)

       SvIOK_on
               Tells an SV that it is an integer.

                       void    SvIOK_on(SV* sv)

       SvIOK_only
               Tells an SV that it is an integer and disables all other "OK"
               bits.

                       void    SvIOK_only(SV* sv)

       SvIOK_only_UV
               Tells an SV that it is an unsigned integer and disables all
               other "OK" bits.

                       void    SvIOK_only_UV(SV* sv)

       SvIOKp  Returns a U32 value indicating whether the SV contains an
               integer.  Checks the private setting.  Use "SvIOK" instead.

                       U32     SvIOKp(SV* sv)

       SvIOK_UV
               Returns a boolean indicating whether the SV contains an integer
               that must be interpreted as unsigned.  A non-negative integer
               whose value is within the range of both an IV and a UV may be
               be flagged as either "SvUOK" or "SVIOK".

                       bool    SvIOK_UV(SV* sv)

       sv_isa  Returns a boolean indicating whether the SV is blessed into the
               specified class.  This does not check for subtypes; use
               "sv_derived_from" to verify an inheritance relationship.

                       int     sv_isa(SV* sv, const char *const name)

       SvIsCOW Returns a U32 value indicating whether the SV is Copy-On-Write
               (either shared hash key scalars, or full Copy On Write scalars
               if 5.9.0 is configured for COW).

                       U32     SvIsCOW(SV* sv)

       SvIsCOW_shared_hash
               Returns a boolean indicating whether the SV is Copy-On-Write
               shared hash key scalar.

                       bool    SvIsCOW_shared_hash(SV* sv)

       sv_isobject
               Returns a boolean indicating whether the SV is an RV pointing
               to a blessed object.  If the SV is not an RV, or if the object
               is not blessed, then this will return false.

                       int     sv_isobject(SV* sv)

       SvIV    Coerces the given SV to IV and returns it.  The returned value
               in many circumstances will get stored in "sv"'s IV slot, but
               not in all cases.  (Use "sv_setiv" to make sure it does).

               See "SvIVx" for a version which guarantees to evaluate "sv"
               only once.

                       IV      SvIV(SV* sv)

       SvIV_nomg
               Like "SvIV" but doesn't process magic.

                       IV      SvIV_nomg(SV* sv)

       SvIV_set
               Set the value of the IV pointer in sv to val.  It is possible
               to perform the same function of this macro with an lvalue
               assignment to "SvIVX".  With future Perls, however, it will be
               more efficient to use "SvIV_set" instead of the lvalue
               assignment to "SvIVX".

                       void    SvIV_set(SV* sv, IV val)

       SvIVX   Returns the raw value in the SV's IV slot, without checks or
               conversions.  Only use when you are sure "SvIOK" is true.  See
               also "SvIV".

                       IV      SvIVX(SV* sv)

       SvIVx   Coerces the given SV to IV and returns it.  The returned value
               in many circumstances will get stored in "sv"'s IV slot, but
               not in all cases.  (Use "sv_setiv" to make sure it does).

               This form guarantees to evaluate "sv" only once.  Only use this
               if "sv" is an expression with side effects, otherwise use the
               more efficient "SvIV".

                       IV      SvIVx(SV* sv)

       SvLEN   Returns the size of the string buffer in the SV, not including
               any part attributable to "SvOOK".  See "SvCUR".

                       STRLEN  SvLEN(SV* sv)

       sv_len  Returns the length of the string in the SV.  Handles magic and
               type coercion and sets the UTF8 flag appropriately.  See also
               "SvCUR", which gives raw access to the "xpv_cur" slot.

                       STRLEN  sv_len(SV *const sv)

       SvLEN_set
               Set the size of the string buffer for the SV. See "SvLEN".

                       void    SvLEN_set(SV* sv, STRLEN len)

       sv_len_utf8
               Returns the number of characters in the string in an SV,
               counting wide UTF-8 bytes as a single character.  Handles magic
               and type coercion.

                       STRLEN  sv_len_utf8(SV *const sv)

       sv_magic
               Adds magic to an SV.  First upgrades "sv" to type "SVt_PVMG" if
               necessary, then adds a new magic item of type "how" to the head
               of the magic list.

               See "sv_magicext" (which "sv_magic" now calls) for a
               description of the handling of the "name" and "namlen"
               arguments.

               You need to use "sv_magicext" to add magic to "SvREADONLY" SVs
               and also to add more than one instance of the same "how".

                       void    sv_magic(SV *const sv, SV *const obj,
                                        const int how, const char *const name,
                                        const I32 namlen)

       sv_magicext
               Adds magic to an SV, upgrading it if necessary.  Applies the
               supplied "vtable" and returns a pointer to the magic added.

               Note that "sv_magicext" will allow things that "sv_magic" will
               not.  In particular, you can add magic to "SvREADONLY" SVs, and
               add more than one instance of the same "how".

               If "namlen" is greater than zero then a "savepvn" copy of
               "name" is stored, if "namlen" is zero then "name" is stored as-
               is and - as another special case - if "(name && namlen ==
               HEf_SVKEY)" then "name" is assumed to contain an SV* and is
               stored as-is with its "REFCNT" incremented.

               (This is now used as a subroutine by "sv_magic".)

                       MAGIC * sv_magicext(SV *const sv, SV *const obj,
                                           const int how,
                                           const MGVTBL *const vtbl,
                                           const char *const name,
                                           const I32 namlen)

       SvMAGIC_set
               Set the value of the MAGIC pointer in "sv" to val.  See
               "SvIV_set".

                       void    SvMAGIC_set(SV* sv, MAGIC* val)

       sv_mortalcopy
               Creates a new SV which is a copy of the original SV (using
               "sv_setsv").  The new SV is marked as mortal.  It will be
               destroyed "soon", either by an explicit call to "FREETMPS", or
               by an implicit call at places such as statement boundaries.
               See also "sv_newmortal" and "sv_2mortal".

                       SV*     sv_mortalcopy(SV *const oldsv)

       sv_newmortal
               Creates a new null SV which is mortal.  The reference count of
               the SV is set to 1.  It will be destroyed "soon", either by an
               explicit call to "FREETMPS", or by an implicit call at places
               such as statement boundaries.  See also "sv_mortalcopy" and
               "sv_2mortal".

                       SV*     sv_newmortal()

       sv_newref
               Increment an SV's reference count.  Use the "SvREFCNT_inc()"
               wrapper instead.

                       SV*     sv_newref(SV *const sv)

       SvNIOK  Returns a U32 value indicating whether the SV contains a
               number, integer or double.

                       U32     SvNIOK(SV* sv)

       SvNIOK_off
               Unsets the NV/IV status of an SV.

                       void    SvNIOK_off(SV* sv)

       SvNIOKp Returns a U32 value indicating whether the SV contains a
               number, integer or double.  Checks the private setting.  Use
               "SvNIOK" instead.

                       U32     SvNIOKp(SV* sv)

       SvNOK   Returns a U32 value indicating whether the SV contains a
               double.

                       U32     SvNOK(SV* sv)

       SvNOK_off
               Unsets the NV status of an SV.

                       void    SvNOK_off(SV* sv)

       SvNOK_on
               Tells an SV that it is a double.

                       void    SvNOK_on(SV* sv)

       SvNOK_only
               Tells an SV that it is a double and disables all other OK bits.

                       void    SvNOK_only(SV* sv)

       SvNOKp  Returns a U32 value indicating whether the SV contains a
               double.  Checks the private setting.  Use "SvNOK" instead.

                       U32     SvNOKp(SV* sv)

       SvNV    Coerces the given SV to NV and returns it.  The returned value
               in many circumstances will get stored in "sv"'s NV slot, but
               not in all cases.  (Use "sv_setnv" to make sure it does).

               See "SvNVx" for a version which guarantees to evaluate "sv"
               only once.

                       NV      SvNV(SV* sv)

       SvNV_nomg
               Like "SvNV" but doesn't process magic.

                       NV      SvNV_nomg(SV* sv)

       SvNV_set
               Set the value of the NV pointer in "sv" to val.  See
               "SvIV_set".

                       void    SvNV_set(SV* sv, NV val)

       SvNVX   Returns the raw value in the SV's NV slot, without checks or
               conversions.  Only use when you are sure "SvNOK" is true.  See
               also "SvNV".

                       NV      SvNVX(SV* sv)

       SvNVx   Coerces the given SV to NV and returns it.  The returned value
               in many circumstances will get stored in "sv"'s NV slot, but
               not in all cases.  (Use "sv_setnv" to make sure it does).

               This form guarantees to evaluate "sv" only once.  Only use this
               if "sv" is an expression with side effects, otherwise use the
               more efficient "SvNV".

                       NV      SvNVx(SV* sv)

       SvOK    Returns a U32 value indicating whether the value is defined.
               This is only meaningful for scalars.

                       U32     SvOK(SV* sv)

       SvOOK   Returns a U32 indicating whether the pointer to the string
               buffer is offset.  This hack is used internally to speed up
               removal of characters from the beginning of a "SvPV".  When
               "SvOOK" is true, then the start of the allocated string buffer
               is actually "SvOOK_offset()" bytes before "SvPVX".  This offset
               used to be stored in "SvIVX", but is now stored within the
               spare part of the buffer.

                       U32     SvOOK(SV* sv)

       SvOOK_offset
               Reads into "len" the offset from "SvPVX" back to the true start
               of the allocated buffer, which will be non-zero if "sv_chop"
               has been used to efficiently remove characters from start of
               the buffer.  Implemented as a macro, which takes the address of
               "len", which must be of type "STRLEN".  Evaluates "sv" more
               than once.  Sets "len" to 0 if "SvOOK(sv)" is false.

                       void    SvOOK_offset(SV*sv, STRLEN len)

       SvPOK   Returns a U32 value indicating whether the SV contains a
               character string.

                       U32     SvPOK(SV* sv)

       SvPOK_off
               Unsets the PV status of an SV.

                       void    SvPOK_off(SV* sv)

       SvPOK_on
               Tells an SV that it is a string.

                       void    SvPOK_on(SV* sv)

       SvPOK_only
               Tells an SV that it is a string and disables all other "OK"
               bits.  Will also turn off the UTF-8 status.

                       void    SvPOK_only(SV* sv)

       SvPOK_only_UTF8
               Tells an SV that it is a string and disables all other "OK"
               bits, and leaves the UTF-8 status as it was.

                       void    SvPOK_only_UTF8(SV* sv)

       SvPOKp  Returns a U32 value indicating whether the SV contains a
               character string.  Checks the private setting.  Use "SvPOK"
               instead.

                       U32     SvPOKp(SV* sv)

       sv_pos_b2u
               Converts the value pointed to by "offsetp" from a count of
               bytes from the start of the string, to a count of the
               equivalent number of UTF-8 chars.  Handles magic and type
               coercion.

               Use "sv_pos_b2u_flags" in preference, which correctly handles
               strings longer than 2Gb.

                       void    sv_pos_b2u(SV *const sv, I32 *const offsetp)

       sv_pos_b2u_flags
               Converts "offset" from a count of bytes from the start of the
               string, to a count of the equivalent number of UTF-8 chars.
               Handles type coercion.  "flags" is passed to "SvPV_flags", and
               usually should be "SV_GMAGIC|SV_CONST_RETURN" to handle magic.

                       STRLEN  sv_pos_b2u_flags(SV *const sv,
                                                STRLEN const offset, U32 flags)

       sv_pos_u2b
               Converts the value pointed to by "offsetp" from a count of
               UTF-8 chars from the start of the string, to a count of the
               equivalent number of bytes; if "lenp" is non-zero, it does the
               same to "lenp", but this time starting from the offset, rather
               than from the start of the string.  Handles magic and type
               coercion.

               Use "sv_pos_u2b_flags" in preference, which correctly handles
               strings longer than 2Gb.

                       void    sv_pos_u2b(SV *const sv, I32 *const offsetp,
                                          I32 *const lenp)

       sv_pos_u2b_flags
               Converts the offset from a count of UTF-8 chars from the start
               of the string, to a count of the equivalent number of bytes; if
               "lenp" is non-zero, it does the same to "lenp", but this time
               starting from "offset", rather than from the start of the
               string.  Handles type coercion.  "flags" is passed to
               "SvPV_flags", and usually should be "SV_GMAGIC|SV_CONST_RETURN"
               to handle magic.

                       STRLEN  sv_pos_u2b_flags(SV *const sv, STRLEN uoffset,
                                                STRLEN *const lenp, U32 flags)

       SvPV    Returns a pointer to the string in the SV, or a stringified
               form of the SV if the SV does not contain a string.  The SV may
               cache the stringified version becoming "SvPOK".  Handles 'get'
               magic.  The "len" variable will be set to the length of the
               string (this is a macro, so don't use &len).  See also "SvPVx"
               for a version which guarantees to evaluate "sv" only once.

               Note that there is no guarantee that the return value of
               "SvPV()" is equal to "SvPVX(sv)", or that "SvPVX(sv)" contains
               valid data, or that successive calls to "SvPV(sv)" will return
               the same pointer value each time.  This is due to the way that
               things like overloading and Copy-On-Write are handled.  In
               these cases, the return value may point to a temporary buffer
               or similar.  If you absolutely need the "SvPVX" field to be
               valid (for example, if you intend to write to it), then see
               "SvPV_force".

                       char*   SvPV(SV* sv, STRLEN len)

       SvPVbyte
               Like "SvPV", but converts "sv" to byte representation first if
               necessary.

                       char*   SvPVbyte(SV* sv, STRLEN len)

       SvPVbyte_force
               Like "SvPV_force", but converts "sv" to byte representation
               first if necessary.

                       char*   SvPVbyte_force(SV* sv, STRLEN len)

       SvPVbyte_nolen
               Like "SvPV_nolen", but converts "sv" to byte representation
               first if necessary.

                       char*   SvPVbyte_nolen(SV* sv)

       sv_pvbyten_force
               The backend for the "SvPVbytex_force" macro.  Always use the
               macro instead.

                       char*   sv_pvbyten_force(SV *const sv, STRLEN *const lp)

       SvPVbytex
               Like "SvPV", but converts "sv" to byte representation first if
               necessary.  Guarantees to evaluate "sv" only once; use the more
               efficient "SvPVbyte" otherwise.

                       char*   SvPVbytex(SV* sv, STRLEN len)

       SvPVbytex_force
               Like "SvPV_force", but converts "sv" to byte representation
               first if necessary.  Guarantees to evaluate "sv" only once; use
               the more efficient "SvPVbyte_force" otherwise.

                       char*   SvPVbytex_force(SV* sv, STRLEN len)

       SvPVCLEAR
               Ensures that sv is a SVt_PV and that its SvCUR is 0, and that
               it is properly null terminated. Equivalent to sv_setpvs(""),
               but more efficient.

                       char *  SvPVCLEAR(SV* sv)

       SvPV_force
               Like "SvPV" but will force the SV into containing a string
               ("SvPOK"), and only a string ("SvPOK_only"), by hook or by
               crook.  You need force if you are going to update the "SvPVX"
               directly.  Processes get magic.

               Note that coercing an arbitrary scalar into a plain PV will
               potentially strip useful data from it.  For example if the SV
               was "SvROK", then the referent will have its reference count
               decremented, and the SV itself may be converted to an "SvPOK"
               scalar with a string buffer containing a value such as
               "ARRAY(0x1234)".

                       char*   SvPV_force(SV* sv, STRLEN len)

       SvPV_force_nomg
               Like "SvPV_force", but doesn't process get magic.

                       char*   SvPV_force_nomg(SV* sv, STRLEN len)

       SvPV_nolen
               Like "SvPV" but doesn't set a length variable.

                       char*   SvPV_nolen(SV* sv)

       SvPV_nomg
               Like "SvPV" but doesn't process magic.

                       char*   SvPV_nomg(SV* sv, STRLEN len)

       SvPV_nomg_nolen
               Like "SvPV_nolen" but doesn't process magic.

                       char*   SvPV_nomg_nolen(SV* sv)

       sv_pvn_force
               Get a sensible string out of the SV somehow.  A private
               implementation of the "SvPV_force" macro for compilers which
               can't cope with complex macro expressions.  Always use the
               macro instead.

                       char*   sv_pvn_force(SV* sv, STRLEN* lp)

       sv_pvn_force_flags
               Get a sensible string out of the SV somehow.  If "flags" has
               the "SV_GMAGIC" bit set, will "mg_get" on "sv" if appropriate,
               else not.  "sv_pvn_force" and "sv_pvn_force_nomg" are
               implemented in terms of this function.  You normally want to
               use the various wrapper macros instead: see "SvPV_force" and
               "SvPV_force_nomg".

                       char*   sv_pvn_force_flags(SV *const sv,
                                                  STRLEN *const lp,
                                                  const I32 flags)

       SvPV_set
               This is probably not what you want to use, you probably wanted
               "sv_usepvn_flags" or "sv_setpvn" or "sv_setpvs".

               Set the value of the PV pointer in "sv" to the Perl allocated
               "NUL"-terminated string "val".  See also "SvIV_set".

               Remember to free the previous PV buffer. There are many things
               to check.  Beware that the existing pointer may be involved in
               copy-on-write or other mischief, so do "SvOOK_off(sv)" and use
               "sv_force_normal" or "SvPV_force" (or check the "SvIsCOW" flag)
               first to make sure this modification is safe. Then finally, if
               it is not a COW, call "SvPV_free" to free the previous PV
               buffer.

                       void    SvPV_set(SV* sv, char* val)

       SvPVutf8
               Like "SvPV", but converts "sv" to UTF-8 first if necessary.

                       char*   SvPVutf8(SV* sv, STRLEN len)

       sv_pvutf8n_force
               The backend for the "SvPVutf8x_force" macro.  Always use the
               macro instead.

                       char*   sv_pvutf8n_force(SV *const sv, STRLEN *const lp)

       SvPVutf8x
               Like "SvPV", but converts "sv" to UTF-8 first if necessary.
               Guarantees to evaluate "sv" only once; use the more efficient
               "SvPVutf8" otherwise.

                       char*   SvPVutf8x(SV* sv, STRLEN len)

       SvPVutf8x_force
               Like "SvPV_force", but converts "sv" to UTF-8 first if
               necessary.  Guarantees to evaluate "sv" only once; use the more
               efficient "SvPVutf8_force" otherwise.

                       char*   SvPVutf8x_force(SV* sv, STRLEN len)

       SvPVutf8_force
               Like "SvPV_force", but converts "sv" to UTF-8 first if
               necessary.

                       char*   SvPVutf8_force(SV* sv, STRLEN len)

       SvPVutf8_nolen
               Like "SvPV_nolen", but converts "sv" to UTF-8 first if
               necessary.

                       char*   SvPVutf8_nolen(SV* sv)

       SvPVX   Returns a pointer to the physical string in the SV.  The SV
               must contain a string.  Prior to 5.9.3 it is not safe to
               execute this macro unless the SV's type >= "SVt_PV".

               This is also used to store the name of an autoloaded subroutine
               in an XS AUTOLOAD routine.  See "Autoloading with XSUBs" in
               perlguts.

                       char*   SvPVX(SV* sv)

       SvPVx   A version of "SvPV" which guarantees to evaluate "sv" only
               once.  Only use this if "sv" is an expression with side
               effects, otherwise use the more efficient "SvPV".

                       char*   SvPVx(SV* sv, STRLEN len)

       SvREADONLY
               Returns true if the argument is readonly, otherwise returns
               false.  Exposed to to perl code via Internals::SvREADONLY().

                       U32     SvREADONLY(SV* sv)

       SvREADONLY_off
               Mark an object as not-readonly. Exactly what this mean depends
               on the object type. Exposed to perl code via
               Internals::SvREADONLY().

                       U32     SvREADONLY_off(SV* sv)

       SvREADONLY_on
               Mark an object as readonly. Exactly what this means depends on
               the object type. Exposed to perl code via
               Internals::SvREADONLY().

                       U32     SvREADONLY_on(SV* sv)

       sv_ref  Returns a SV describing what the SV passed in is a reference
               to.

               dst can be a SV to be set to the description or NULL, in which
               case a mortal SV is returned.

               If ob is true and the SV is blessed, the description is the
               class name, otherwise it is the type of the SV, "SCALAR",
               "ARRAY" etc.

                       SV*     sv_ref(SV *dst, const SV *const sv,
                                      const int ob)

       SvREFCNT
               Returns the value of the object's reference count. Exposed to
               perl code via Internals::SvREFCNT().

                       U32     SvREFCNT(SV* sv)

       SvREFCNT_dec
               Decrements the reference count of the given SV.  "sv" may be
               "NULL".

                       void    SvREFCNT_dec(SV* sv)

       SvREFCNT_dec_NN
               Same as "SvREFCNT_dec", but can only be used if you know "sv"
               is not "NULL".  Since we don't have to check the NULLness, it's
               faster and smaller.

                       void    SvREFCNT_dec_NN(SV* sv)

       SvREFCNT_inc
               Increments the reference count of the given SV, returning the
               SV.

               All of the following "SvREFCNT_inc"* macros are optimized
               versions of "SvREFCNT_inc", and can be replaced with
               "SvREFCNT_inc".

                       SV*     SvREFCNT_inc(SV* sv)

       SvREFCNT_inc_NN
               Same as "SvREFCNT_inc", but can only be used if you know "sv"
               is not "NULL".  Since we don't have to check the NULLness, it's
               faster and smaller.

                       SV*     SvREFCNT_inc_NN(SV* sv)

       SvREFCNT_inc_simple
               Same as "SvREFCNT_inc", but can only be used with expressions
               without side effects.  Since we don't have to store a temporary
               value, it's faster.

                       SV*     SvREFCNT_inc_simple(SV* sv)

       SvREFCNT_inc_simple_NN
               Same as "SvREFCNT_inc_simple", but can only be used if you know
               "sv" is not "NULL".  Since we don't have to check the NULLness,
               it's faster and smaller.

                       SV*     SvREFCNT_inc_simple_NN(SV* sv)

       SvREFCNT_inc_simple_void
               Same as "SvREFCNT_inc_simple", but can only be used if you
               don't need the return value.  The macro doesn't need to return
               a meaningful value.

                       void    SvREFCNT_inc_simple_void(SV* sv)

       SvREFCNT_inc_simple_void_NN
               Same as "SvREFCNT_inc", but can only be used if you don't need
               the return value, and you know that "sv" is not "NULL".  The
               macro doesn't need to return a meaningful value, or check for
               NULLness, so it's smaller and faster.

                       void    SvREFCNT_inc_simple_void_NN(SV* sv)

       SvREFCNT_inc_void
               Same as "SvREFCNT_inc", but can only be used if you don't need
               the return value.  The macro doesn't need to return a
               meaningful value.

                       void    SvREFCNT_inc_void(SV* sv)

       SvREFCNT_inc_void_NN
               Same as "SvREFCNT_inc", but can only be used if you don't need
               the return value, and you know that "sv" is not "NULL".  The
               macro doesn't need to return a meaningful value, or check for
               NULLness, so it's smaller and faster.

                       void    SvREFCNT_inc_void_NN(SV* sv)

       sv_reftype
               Returns a string describing what the SV is a reference to.

               If ob is true and the SV is blessed, the string is the class
               name, otherwise it is the type of the SV, "SCALAR", "ARRAY"
               etc.

                       const char* sv_reftype(const SV *const sv, const int ob)

       sv_replace
               Make the first argument a copy of the second, then delete the
               original.  The target SV physically takes over ownership of the
               body of the source SV and inherits its flags; however, the
               target keeps any magic it owns, and any magic in the source is
               discarded.  Note that this is a rather specialist SV copying
               operation; most of the time you'll want to use "sv_setsv" or
               one of its many macro front-ends.

                       void    sv_replace(SV *const sv, SV *const nsv)

       sv_report_used
               Dump the contents of all SVs not yet freed (debugging aid).

                       void    sv_report_used()

       sv_reset
               Underlying implementation for the "reset" Perl function.  Note
               that the perl-level function is vaguely deprecated.

                       void    sv_reset(const char* s, HV *const stash)

       SvROK   Tests if the SV is an RV.

                       U32     SvROK(SV* sv)

       SvROK_off
               Unsets the RV status of an SV.

                       void    SvROK_off(SV* sv)

       SvROK_on
               Tells an SV that it is an RV.

                       void    SvROK_on(SV* sv)

       SvRV    Dereferences an RV to return the SV.

                       SV*     SvRV(SV* sv)

       SvRV_set
               Set the value of the RV pointer in "sv" to val.  See
               "SvIV_set".

                       void    SvRV_set(SV* sv, SV* val)

       sv_rvunweaken
               Unweaken a reference: Clear the "SvWEAKREF" flag on this RV;
               remove the backreference to this RV from the array of
               backreferences associated with the target SV, increment the
               refcount of the target.  Silently ignores "undef" and warns on
               non-weak references.

                       SV*     sv_rvunweaken(SV *const sv)

       sv_rvweaken
               Weaken a reference: set the "SvWEAKREF" flag on this RV; give
               the referred-to SV "PERL_MAGIC_backref" magic if it hasn't
               already; and push a back-reference to this RV onto the array of
               backreferences associated with that magic.  If the RV is
               magical, set magic will be called after the RV is cleared.
               Silently ignores "undef" and warns on already-weak references.

                       SV*     sv_rvweaken(SV *const sv)

       sv_setiv
               Copies an integer into the given SV, upgrading first if
               necessary.  Does not handle 'set' magic.  See also
               "sv_setiv_mg".

                       void    sv_setiv(SV *const sv, const IV num)

       sv_setiv_mg
               Like "sv_setiv", but also handles 'set' magic.

                       void    sv_setiv_mg(SV *const sv, const IV i)

       sv_setnv
               Copies a double into the given SV, upgrading first if
               necessary.  Does not handle 'set' magic.  See also
               "sv_setnv_mg".

                       void    sv_setnv(SV *const sv, const NV num)

       sv_setnv_mg
               Like "sv_setnv", but also handles 'set' magic.

                       void    sv_setnv_mg(SV *const sv, const NV num)

       sv_setpv
               Copies a string into an SV.  The string must be terminated with
               a "NUL" character, and not contain embeded "NUL"'s.  Does not
               handle 'set' magic.  See "sv_setpv_mg".

                       void    sv_setpv(SV *const sv, const char *const ptr)

       sv_setpvf
               Works like "sv_catpvf" but copies the text into the SV instead
               of appending it.  Does not handle 'set' magic.  See
               "sv_setpvf_mg".

                       void    sv_setpvf(SV *const sv, const char *const pat,
                                         ...)

       sv_setpvf_mg
               Like "sv_setpvf", but also handles 'set' magic.

                       void    sv_setpvf_mg(SV *const sv,
                                            const char *const pat, ...)

       sv_setpviv
               Copies an integer into the given SV, also updating its string
               value.  Does not handle 'set' magic.  See "sv_setpviv_mg".

                       void    sv_setpviv(SV *const sv, const IV num)

       sv_setpviv_mg
               Like "sv_setpviv", but also handles 'set' magic.

                       void    sv_setpviv_mg(SV *const sv, const IV iv)

       sv_setpvn
               Copies a string (possibly containing embedded "NUL" characters)
               into an SV.  The "len" parameter indicates the number of bytes
               to be copied.  If the "ptr" argument is NULL the SV will become
               undefined.  Does not handle 'set' magic.  See "sv_setpvn_mg".

                       void    sv_setpvn(SV *const sv, const char *const ptr,
                                         const STRLEN len)

       sv_setpvn_mg
               Like "sv_setpvn", but also handles 'set' magic.

                       void    sv_setpvn_mg(SV *const sv,
                                            const char *const ptr,
                                            const STRLEN len)

       sv_setpvs
               Like "sv_setpvn", but takes a literal string instead of a
               string/length pair.

                       void    sv_setpvs(SV* sv, "literal string" s)

       sv_setpvs_mg
               Like "sv_setpvn_mg", but takes a literal string instead of a
               string/length pair.

                       void    sv_setpvs_mg(SV* sv, "literal string" s)

       sv_setpv_bufsize
               Sets the SV to be a string of cur bytes length, with at least
               len bytes available. Ensures that there is a null byte at
               SvEND.  Returns a char * pointer to the SvPV buffer.

                       char  * sv_setpv_bufsize(SV *const sv, const STRLEN cur,
                                                const STRLEN len)

       sv_setpv_mg
               Like "sv_setpv", but also handles 'set' magic.

                       void    sv_setpv_mg(SV *const sv, const char *const ptr)

       sv_setref_iv
               Copies an integer into a new SV, optionally blessing the SV.
               The "rv" argument will be upgraded to an RV.  That RV will be
               modified to point to the new SV.  The "classname" argument
               indicates the package for the blessing.  Set "classname" to
               "NULL" to avoid the blessing.  The new SV will have a reference
               count of 1, and the RV will be returned.

                       SV*     sv_setref_iv(SV *const rv,
                                            const char *const classname,
                                            const IV iv)

       sv_setref_nv
               Copies a double into a new SV, optionally blessing the SV.  The
               "rv" argument will be upgraded to an RV.  That RV will be
               modified to point to the new SV.  The "classname" argument
               indicates the package for the blessing.  Set "classname" to
               "NULL" to avoid the blessing.  The new SV will have a reference
               count of 1, and the RV will be returned.

                       SV*     sv_setref_nv(SV *const rv,
                                            const char *const classname,
                                            const NV nv)

       sv_setref_pv
               Copies a pointer into a new SV, optionally blessing the SV.
               The "rv" argument will be upgraded to an RV.  That RV will be
               modified to point to the new SV.  If the "pv" argument is
               "NULL", then "PL_sv_undef" will be placed into the SV.  The
               "classname" argument indicates the package for the blessing.
               Set "classname" to "NULL" to avoid the blessing.  The new SV
               will have a reference count of 1, and the RV will be returned.

               Do not use with other Perl types such as HV, AV, SV, CV,
               because those objects will become corrupted by the pointer copy
               process.

               Note that "sv_setref_pvn" copies the string while this copies
               the pointer.

                       SV*     sv_setref_pv(SV *const rv,
                                            const char *const classname,
                                            void *const pv)

       sv_setref_pvn
               Copies a string into a new SV, optionally blessing the SV.  The
               length of the string must be specified with "n".  The "rv"
               argument will be upgraded to an RV.  That RV will be modified
               to point to the new SV.  The "classname" argument indicates the
               package for the blessing.  Set "classname" to "NULL" to avoid
               the blessing.  The new SV will have a reference count of 1, and
               the RV will be returned.

               Note that "sv_setref_pv" copies the pointer while this copies
               the string.

                       SV*     sv_setref_pvn(SV *const rv,
                                             const char *const classname,
                                             const char *const pv,
                                             const STRLEN n)

       sv_setref_pvs
               Like "sv_setref_pvn", but takes a literal string instead of a
               string/length pair.

                       SV *    sv_setref_pvs("literal string" s)

       sv_setref_uv
               Copies an unsigned integer into a new SV, optionally blessing
               the SV.  The "rv" argument will be upgraded to an RV.  That RV
               will be modified to point to the new SV.  The "classname"
               argument indicates the package for the blessing.  Set
               "classname" to "NULL" to avoid the blessing.  The new SV will
               have a reference count of 1, and the RV will be returned.

                       SV*     sv_setref_uv(SV *const rv,
                                            const char *const classname,
                                            const UV uv)

       sv_setsv
               Copies the contents of the source SV "ssv" into the destination
               SV "dsv".  The source SV may be destroyed if it is mortal, so
               don't use this function if the source SV needs to be reused.
               Does not handle 'set' magic on destination SV.  Calls 'get'
               magic on source SV.  Loosely speaking, it performs a copy-by-
               value, obliterating any previous content of the destination.

               You probably want to use one of the assortment of wrappers,
               such as "SvSetSV", "SvSetSV_nosteal", "SvSetMagicSV" and
               "SvSetMagicSV_nosteal".

                       void    sv_setsv(SV *dstr, SV *sstr)

       sv_setsv_flags
               Copies the contents of the source SV "ssv" into the destination
               SV "dsv".  The source SV may be destroyed if it is mortal, so
               don't use this function if the source SV needs to be reused.
               Does not handle 'set' magic.  Loosely speaking, it performs a
               copy-by-value, obliterating any previous content of the
               destination.  If the "flags" parameter has the "SV_GMAGIC" bit
               set, will "mg_get" on "ssv" if appropriate, else not.  If the
               "flags" parameter has the "SV_NOSTEAL" bit set then the buffers
               of temps will not be stolen.  "sv_setsv" and "sv_setsv_nomg"
               are implemented in terms of this function.

               You probably want to use one of the assortment of wrappers,
               such as "SvSetSV", "SvSetSV_nosteal", "SvSetMagicSV" and
               "SvSetMagicSV_nosteal".

               This is the primary function for copying scalars, and most
               other copy-ish functions and macros use this underneath.

                       void    sv_setsv_flags(SV *dstr, SV *sstr,
                                              const I32 flags)

       sv_setsv_mg
               Like "sv_setsv", but also handles 'set' magic.

                       void    sv_setsv_mg(SV *const dstr, SV *const sstr)

       sv_setsv_nomg
               Like "sv_setsv" but doesn't process magic.

                       void    sv_setsv_nomg(SV* dsv, SV* ssv)

       sv_setuv
               Copies an unsigned integer into the given SV, upgrading first
               if necessary.  Does not handle 'set' magic.  See also
               "sv_setuv_mg".

                       void    sv_setuv(SV *const sv, const UV num)

       sv_setuv_mg
               Like "sv_setuv", but also handles 'set' magic.

                       void    sv_setuv_mg(SV *const sv, const UV u)

       sv_set_undef
               Equivalent to "sv_setsv(sv, &PL_sv_undef)", but more efficient.
               Doesn't handle set magic.

               The perl equivalent is "$sv = undef;". Note that it doesn't
               free any string buffer, unlike "undef $sv".

               Introduced in perl 5.25.12.

                       void    sv_set_undef(SV *sv)

       SvSTASH Returns the stash of the SV.

                       HV*     SvSTASH(SV* sv)

       SvSTASH_set
               Set the value of the STASH pointer in "sv" to val.  See
               "SvIV_set".

                       void    SvSTASH_set(SV* sv, HV* val)

       SvTAINT Taints an SV if tainting is enabled, and if some input to the
               current expression is tainted--usually a variable, but possibly
               also implicit inputs such as locale settings.  "SvTAINT"
               propagates that taintedness to the outputs of an expression in
               a pessimistic fashion; i.e., without paying attention to
               precisely which outputs are influenced by which inputs.

                       void    SvTAINT(SV* sv)

       SvTAINTED
               Checks to see if an SV is tainted.  Returns TRUE if it is,
               FALSE if not.

                       bool    SvTAINTED(SV* sv)

       sv_tainted
               Test an SV for taintedness.  Use "SvTAINTED" instead.

                       bool    sv_tainted(SV *const sv)

       SvTAINTED_off
               Untaints an SV.  Be very careful with this routine, as it
               short-circuits some of Perl's fundamental security features.
               XS module authors should not use this function unless they
               fully understand all the implications of unconditionally
               untainting the value.  Untainting should be done in the
               standard perl fashion, via a carefully crafted regexp, rather
               than directly untainting variables.

                       void    SvTAINTED_off(SV* sv)

       SvTAINTED_on
               Marks an SV as tainted if tainting is enabled.

                       void    SvTAINTED_on(SV* sv)

       SvTRUE  Returns a boolean indicating whether Perl would evaluate the SV
               as true or false.  See "SvOK" for a defined/undefined test.
               Handles 'get' magic unless the scalar is already "SvPOK",
               "SvIOK" or "SvNOK" (the public, not the private flags).

                       bool    SvTRUE(SV* sv)

       sv_true Returns true if the SV has a true value by Perl's rules.  Use
               the "SvTRUE" macro instead, which may call "sv_true()" or may
               instead use an in-line version.

                       I32     sv_true(SV *const sv)

       SvTRUE_nomg
               Returns a boolean indicating whether Perl would evaluate the SV
               as true or false.  See "SvOK" for a defined/undefined test.
               Does not handle 'get' magic.

                       bool    SvTRUE_nomg(SV* sv)

       SvTYPE  Returns the type of the SV.  See "svtype".

                       svtype  SvTYPE(SV* sv)

       sv_unmagic
               Removes all magic of type "type" from an SV.

                       int     sv_unmagic(SV *const sv, const int type)

       sv_unmagicext
               Removes all magic of type "type" with the specified "vtbl" from
               an SV.

                       int     sv_unmagicext(SV *const sv, const int type,
                                             MGVTBL *vtbl)

       sv_unref_flags
               Unsets the RV status of the SV, and decrements the reference
               count of whatever was being referenced by the RV.  This can
               almost be thought of as a reversal of "newSVrv".  The "cflags"
               argument can contain "SV_IMMEDIATE_UNREF" to force the
               reference count to be decremented (otherwise the decrementing
               is conditional on the reference count being different from one
               or the reference being a readonly SV).  See "SvROK_off".

                       void    sv_unref_flags(SV *const ref, const U32 flags)

       sv_untaint
               Untaint an SV.  Use "SvTAINTED_off" instead.

                       void    sv_untaint(SV *const sv)

       SvUOK   Returns a boolean indicating whether the SV contains an integer
               that must be interpreted as unsigned.  A non-negative integer
               whose value is within the range of both an IV and a UV may be
               be flagged as either "SvUOK" or "SVIOK".

                       bool    SvUOK(SV* sv)

       SvUPGRADE
               Used to upgrade an SV to a more complex form.  Uses
               "sv_upgrade" to perform the upgrade if necessary.  See
               "svtype".

                       void    SvUPGRADE(SV* sv, svtype type)

       sv_upgrade
               Upgrade an SV to a more complex form.  Generally adds a new
               body type to the SV, then copies across as much information as
               possible from the old body.  It croaks if the SV is already in
               a more complex form than requested.  You generally want to use
               the "SvUPGRADE" macro wrapper, which checks the type before
               calling "sv_upgrade", and hence does not croak.  See also
               "svtype".

                       void    sv_upgrade(SV *const sv, svtype new_type)

       sv_usepvn_flags
               Tells an SV to use "ptr" to find its string value.  Normally
               the string is stored inside the SV, but sv_usepvn allows the SV
               to use an outside string.  "ptr" should point to memory that
               was allocated by "Newx".  It must be the start of a "Newx"-ed
               block of memory, and not a pointer to the middle of it (beware
               of "OOK" and copy-on-write), and not be from a non-"Newx"
               memory allocator like "malloc".  The string length, "len", must
               be supplied.  By default this function will "Renew" (i.e.
               realloc, move) the memory pointed to by "ptr", so that pointer
               should not be freed or used by the programmer after giving it
               to "sv_usepvn", and neither should any pointers from "behind"
               that pointer (e.g. ptr + 1) be used.

               If "flags&SV_SMAGIC" is true, will call "SvSETMAGIC".  If
               "flags&SV_HAS_TRAILING_NUL" is true, then "ptr[len]" must be
               "NUL", and the realloc will be skipped (i.e. the buffer is
               actually at least 1 byte longer than "len", and already meets
               the requirements for storing in "SvPVX").

                       void    sv_usepvn_flags(SV *const sv, char* ptr,
                                               const STRLEN len,
                                               const U32 flags)

       SvUTF8  Returns a U32 value indicating the UTF-8 status of an SV.  If
               things are set-up properly, this indicates whether or not the
               SV contains UTF-8 encoded data.  You should use this after a
               call to "SvPV()" or one of its variants, in case any call to
               string overloading updates the internal flag.

               If you want to take into account the bytes pragma, use
               "DO_UTF8" instead.

                       U32     SvUTF8(SV* sv)

       sv_utf8_decode
               If the PV of the SV is an octet sequence in Perl's extended
               UTF-8 and contains a multiple-byte character, the "SvUTF8" flag
               is turned on so that it looks like a character.  If the PV
               contains only single-byte characters, the "SvUTF8" flag stays
               off.  Scans PV for validity and returns FALSE if the PV is
               invalid UTF-8.

                       bool    sv_utf8_decode(SV *const sv)

       sv_utf8_downgrade
               Attempts to convert the PV of an SV from characters to bytes.
               If the PV contains a character that cannot fit in a byte, this
               conversion will fail; in this case, either returns false or, if
               "fail_ok" is not true, croaks.

               This is not a general purpose Unicode to byte encoding
               interface: use the "Encode" extension for that.

                       bool    sv_utf8_downgrade(SV *const sv,
                                                 const bool fail_ok)

       sv_utf8_encode
               Converts the PV of an SV to UTF-8, but then turns the "SvUTF8"
               flag off so that it looks like octets again.

                       void    sv_utf8_encode(SV *const sv)

       sv_utf8_upgrade
               Converts the PV of an SV to its UTF-8-encoded form.  Forces the
               SV to string form if it is not already.  Will "mg_get" on "sv"
               if appropriate.  Always sets the "SvUTF8" flag to avoid future
               validity checks even if the whole string is the same in UTF-8
               as not.  Returns the number of bytes in the converted string

               This is not a general purpose byte encoding to Unicode
               interface: use the Encode extension for that.

                       STRLEN  sv_utf8_upgrade(SV *sv)

       sv_utf8_upgrade_flags
               Converts the PV of an SV to its UTF-8-encoded form.  Forces the
               SV to string form if it is not already.  Always sets the SvUTF8
               flag to avoid future validity checks even if all the bytes are
               invariant in UTF-8.  If "flags" has "SV_GMAGIC" bit set, will
               "mg_get" on "sv" if appropriate, else not.

               The "SV_FORCE_UTF8_UPGRADE" flag is now ignored.

               Returns the number of bytes in the converted string.

               This is not a general purpose byte encoding to Unicode
               interface: use the Encode extension for that.

                       STRLEN  sv_utf8_upgrade_flags(SV *const sv,
                                                     const I32 flags)

       sv_utf8_upgrade_flags_grow
               Like "sv_utf8_upgrade_flags", but has an additional parameter
               "extra", which is the number of unused bytes the string of "sv"
               is guaranteed to have free after it upon return.  This allows
               the caller to reserve extra space that it intends to fill, to
               avoid extra grows.

               "sv_utf8_upgrade", "sv_utf8_upgrade_nomg", and
               "sv_utf8_upgrade_flags" are implemented in terms of this
               function.

               Returns the number of bytes in the converted string (not
               including the spares).

                       STRLEN  sv_utf8_upgrade_flags_grow(SV *const sv,
                                                          const I32 flags,
                                                          STRLEN extra)

       sv_utf8_upgrade_nomg
               Like "sv_utf8_upgrade", but doesn't do magic on "sv".

                       STRLEN  sv_utf8_upgrade_nomg(SV *sv)

       SvUTF8_off
               Unsets the UTF-8 status of an SV (the data is not changed, just
               the flag).  Do not use frivolously.

                       void    SvUTF8_off(SV *sv)

       SvUTF8_on
               Turn on the UTF-8 status of an SV (the data is not changed,
               just the flag).  Do not use frivolously.

                       void    SvUTF8_on(SV *sv)

       SvUV    Coerces the given SV to UV and returns it.  The returned value
               in many circumstances will get stored in "sv"'s UV slot, but
               not in all cases.  (Use "sv_setuv" to make sure it does).

               See "SvUVx" for a version which guarantees to evaluate "sv"
               only once.

                       UV      SvUV(SV* sv)

       SvUV_nomg
               Like "SvUV" but doesn't process magic.

                       UV      SvUV_nomg(SV* sv)

       SvUV_set
               Set the value of the UV pointer in "sv" to val.  See
               "SvIV_set".

                       void    SvUV_set(SV* sv, UV val)

       SvUVX   Returns the raw value in the SV's UV slot, without checks or
               conversions.  Only use when you are sure "SvIOK" is true.  See
               also "SvUV".

                       UV      SvUVX(SV* sv)

       SvUVx   Coerces the given SV to UV and returns it.  The returned value
               in many circumstances will get stored in "sv"'s UV slot, but
               not in all cases.  (Use "sv_setuv" to make sure it does).

               This form guarantees to evaluate "sv" only once.  Only use this
               if "sv" is an expression with side effects, otherwise use the
               more efficient "SvUV".

                       UV      SvUVx(SV* sv)

       sv_vcatpvf
               Processes its arguments like "sv_vcatpvfn" called with a non-
               null C-style variable argument list, and appends the formatted
               output to an SV.  Does not handle 'set' magic.  See
               "sv_vcatpvf_mg".

               Usually used via its frontend "sv_catpvf".

                       void    sv_vcatpvf(SV *const sv, const char *const pat,
                                          va_list *const args)

       sv_vcatpvfn
                       void    sv_vcatpvfn(SV *const sv, const char *const pat,
                                           const STRLEN patlen,
                                           va_list *const args,
                                           SV **const svargs,
                                           const Size_t sv_count,
                                           bool *const maybe_tainted)

       sv_vcatpvfn_flags
               Processes its arguments like "vsprintf" and appends the
               formatted output to an SV.  Uses an array of SVs if the C-style
               variable argument list is missing ("NULL"). Argument reordering
               (using format specifiers like "%2$d" or "%*2$d") is supported
               only when using an array of SVs; using a C-style "va_list"
               argument list with a format string that uses argument
               reordering will yield an exception.

               When running with taint checks enabled, indicates via
               "maybe_tainted" if results are untrustworthy (often due to the
               use of locales).

               If called as "sv_vcatpvfn" or flags has the "SV_GMAGIC" bit
               set, calls get magic.

               It assumes that pat has the same utf8-ness as sv.  It's the
               caller's responsibility to ensure that this is so.

               Usually used via one of its frontends "sv_vcatpvf" and
               "sv_vcatpvf_mg".

                       void    sv_vcatpvfn_flags(SV *const sv,
                                                 const char *const pat,
                                                 const STRLEN patlen,
                                                 va_list *const args,
                                                 SV **const svargs,
                                                 const Size_t sv_count,
                                                 bool *const maybe_tainted,
                                                 const U32 flags)

       sv_vcatpvf_mg
               Like "sv_vcatpvf", but also handles 'set' magic.

               Usually used via its frontend "sv_catpvf_mg".

                       void    sv_vcatpvf_mg(SV *const sv,
                                             const char *const pat,
                                             va_list *const args)

       SvVOK   Returns a boolean indicating whether the SV contains a
               v-string.

                       bool    SvVOK(SV* sv)

       sv_vsetpvf
               Works like "sv_vcatpvf" but copies the text into the SV instead
               of appending it.  Does not handle 'set' magic.  See
               "sv_vsetpvf_mg".

               Usually used via its frontend "sv_setpvf".

                       void    sv_vsetpvf(SV *const sv, const char *const pat,
                                          va_list *const args)

       sv_vsetpvfn
               Works like "sv_vcatpvfn" but copies the text into the SV
               instead of appending it.

               Usually used via one of its frontends "sv_vsetpvf" and
               "sv_vsetpvf_mg".

                       void    sv_vsetpvfn(SV *const sv, const char *const pat,
                                           const STRLEN patlen,
                                           va_list *const args,
                                           SV **const svargs,
                                           const Size_t sv_count,
                                           bool *const maybe_tainted)

       sv_vsetpvf_mg
               Like "sv_vsetpvf", but also handles 'set' magic.

               Usually used via its frontend "sv_setpvf_mg".

                       void    sv_vsetpvf_mg(SV *const sv,
                                             const char *const pat,
                                             va_list *const args)

Unicode Support
       "Unicode Support" in perlguts has an introduction to this API.

       See also "Character classification", and "Character case changing".
       Various functions outside this section also work specially with
       Unicode.  Search for the string "utf8" in this document.

       BOM_UTF8
               This is a macro that evaluates to a string constant of the
               UTF-8 bytes that define the Unicode BYTE ORDER MARK (U+FEFF)
               for the platform that perl is compiled on.  This allows code to
               use a mnemonic for this character that works on both ASCII and
               EBCDIC platforms.  "sizeof(BOM_UTF8)-1" can be used to get its
               length in bytes.

       bytes_cmp_utf8
               Compares the sequence of characters (stored as octets) in "b",
               "blen" with the sequence of characters (stored as UTF-8) in
               "u", "ulen".  Returns 0 if they are equal, -1 or -2 if the
               first string is less than the second string, +1 or +2 if the
               first string is greater than the second string.

               -1 or +1 is returned if the shorter string was identical to the
               start of the longer string.  -2 or +2 is returned if there was
               a difference between characters within the strings.

                       int     bytes_cmp_utf8(const U8 *b, STRLEN blen,
                                              const U8 *u, STRLEN ulen)

       bytes_from_utf8
               NOTE: this function is experimental and may change or be
               removed without notice.

               Converts a potentially UTF-8 encoded string "s" of length *lenp
               into native byte encoding.  On input, the boolean *is_utf8p
               gives whether or not "s" is actually encoded in UTF-8.

               Unlike "utf8_to_bytes" but like "bytes_to_utf8", this is non-
               destructive of the input string.

               Do nothing if *is_utf8p is 0, or if there are code points in
               the string not expressible in native byte encoding.  In these
               cases, *is_utf8p and *lenp are unchanged, and the return value
               is the original "s".

               Otherwise, *is_utf8p is set to 0, and the return value is a
               pointer to a newly created string containing a downgraded copy
               of "s", and whose length is returned in *lenp, updated.  The
               new string is "NUL"-terminated.  The caller is responsible for
               arranging for the memory used by this string to get freed.

               Upon successful return, the number of variants in the string
               can be computed by having saved the value of *lenp before the
               call, and subtracting the after-call value of *lenp from it.

                       U8*     bytes_from_utf8(const U8 *s, STRLEN *lenp,
                                               bool *is_utf8p)

       bytes_to_utf8
               NOTE: this function is experimental and may change or be
               removed without notice.

               Converts a string "s" of length *lenp bytes from the native
               encoding into UTF-8.  Returns a pointer to the newly-created
               string, and sets *lenp to reflect the new length in bytes.  The
               caller is responsible for arranging for the memory used by this
               string to get freed.

               Upon successful return, the number of variants in the string
               can be computed by having saved the value of *lenp before the
               call, and subtracting it from the after-call value of *lenp.

               A "NUL" character will be written after the end of the string.

               If you want to convert to UTF-8 from encodings other than the
               native (Latin1 or EBCDIC), see "sv_recode_to_utf8"().

                       U8*     bytes_to_utf8(const U8 *s, STRLEN *lenp)

       DO_UTF8 Returns a bool giving whether or not the PV in "sv" is to be
               treated as being encoded in UTF-8.

               You should use this after a call to "SvPV()" or one of its
               variants, in case any call to string overloading updates the
               internal UTF-8 encoding flag.

                       bool    DO_UTF8(SV* sv)

       foldEQ_utf8
               Returns true if the leading portions of the strings "s1" and
               "s2" (either or both of which may be in UTF-8) are the same
               case-insensitively; false otherwise.  How far into the strings
               to compare is determined by other input parameters.

               If "u1" is true, the string "s1" is assumed to be in
               UTF-8-encoded Unicode; otherwise it is assumed to be in native
               8-bit encoding.  Correspondingly for "u2" with respect to "s2".

               If the byte length "l1" is non-zero, it says how far into "s1"
               to check for fold equality.  In other words, "s1"+"l1" will be
               used as a goal to reach.  The scan will not be considered to be
               a match unless the goal is reached, and scanning won't continue
               past that goal.  Correspondingly for "l2" with respect to "s2".

               If "pe1" is non-"NULL" and the pointer it points to is not
               "NULL", that pointer is considered an end pointer to the
               position 1 byte past the maximum point in "s1" beyond which
               scanning will not continue under any circumstances.  (This
               routine assumes that UTF-8 encoded input strings are not
               malformed; malformed input can cause it to read past "pe1").
               This means that if both "l1" and "pe1" are specified, and "pe1"
               is less than "s1"+"l1", the match will never be successful
               because it can never get as far as its goal (and in fact is
               asserted against).  Correspondingly for "pe2" with respect to
               "s2".

               At least one of "s1" and "s2" must have a goal (at least one of
               "l1" and "l2" must be non-zero), and if both do, both have to
               be reached for a successful match.   Also, if the fold of a
               character is multiple characters, all of them must be matched
               (see tr21 reference below for 'folding').

               Upon a successful match, if "pe1" is non-"NULL", it will be set
               to point to the beginning of the next character of "s1" beyond
               what was matched.  Correspondingly for "pe2" and "s2".

               For case-insensitiveness, the "casefolding" of Unicode is used
               instead of upper/lowercasing both the characters, see
               <http://www.unicode.org/unicode/reports/tr21/> (Case Mappings).

                       I32     foldEQ_utf8(const char *s1, char **pe1, UV l1,
                                           bool u1, const char *s2, char **pe2,
                                           UV l2, bool u2)

       is_ascii_string
               This is a misleadingly-named synonym for
               "is_utf8_invariant_string".  On ASCII-ish platforms, the name
               isn't misleading: the ASCII-range characters are exactly the
               UTF-8 invariants.  But EBCDIC machines have more invariants
               than just the ASCII characters, so "is_utf8_invariant_string"
               is preferred.

                       bool    is_ascii_string(const U8* const s, STRLEN len)

       is_c9strict_utf8_string
               Returns TRUE if the first "len" bytes of string "s" form a
               valid UTF-8-encoded string that conforms to Unicode Corrigendum
               #9 <http://www.unicode.org/versions/corrigendum9.html>;
               otherwise it returns FALSE.  If "len" is 0, it will be
               calculated using strlen(s) (which means if you use this option,
               that "s" can't have embedded "NUL" characters and has to have a
               terminating "NUL" byte).  Note that all characters being ASCII
               constitute 'a valid UTF-8 string'.

               This function returns FALSE for strings containing any code
               points above the Unicode max of 0x10FFFF or surrogate code
               points, but accepts non-character code points per Corrigendum
               #9 <http://www.unicode.org/versions/corrigendum9.html>.

               See also "is_utf8_invariant_string",
               "is_utf8_invariant_string_loc", "is_utf8_string",
               "is_utf8_string_flags", "is_utf8_string_loc",
               "is_utf8_string_loc_flags", "is_utf8_string_loclen",
               "is_utf8_string_loclen_flags", "is_utf8_fixed_width_buf_flags",
               "is_utf8_fixed_width_buf_loc_flags",
               "is_utf8_fixed_width_buf_loclen_flags",
               "is_strict_utf8_string", "is_strict_utf8_string_loc",
               "is_strict_utf8_string_loclen", "is_c9strict_utf8_string_loc",
               and "is_c9strict_utf8_string_loclen".

                       bool    is_c9strict_utf8_string(const U8 *s, STRLEN len)

       is_c9strict_utf8_string_loc
               Like "is_c9strict_utf8_string" but stores the location of the
               failure (in the case of "utf8ness failure") or the location
               "s"+"len" (in the case of "utf8ness success") in the "ep"
               pointer.

               See also "is_c9strict_utf8_string_loclen".

                       bool    is_c9strict_utf8_string_loc(const U8 *s,
                                                           STRLEN len,
                                                           const U8 **ep)

       is_c9strict_utf8_string_loclen
               Like "is_c9strict_utf8_string" but stores the location of the
               failure (in the case of "utf8ness failure") or the location
               "s"+"len" (in the case of "utf8ness success") in the "ep"
               pointer, and the number of UTF-8 encoded characters in the "el"
               pointer.

               See also "is_c9strict_utf8_string_loc".

                       bool    is_c9strict_utf8_string_loclen(const U8 *s,
                                                              STRLEN len,
                                                              const U8 **ep,
                                                              STRLEN *el)

       isC9_STRICT_UTF8_CHAR
               Evaluates to non-zero if the first few bytes of the string
               starting at "s" and looking no further than "e-1" are well-
               formed UTF-8 that represents some Unicode non-surrogate code
               point; otherwise it evaluates to 0.  If non-zero, the value
               gives how many bytes starting at "s" comprise the code point's
               representation.  Any bytes remaining before "e", but beyond the
               ones needed to form the first code point in "s", are not
               examined.

               The largest acceptable code point is the Unicode maximum
               0x10FFFF.  This differs from "isSTRICT_UTF8_CHAR" only in that
               it accepts non-character code points.  This corresponds to
               Unicode Corrigendum #9
               <http://www.unicode.org/versions/corrigendum9.html>.  which
               said that non-character code points are merely discouraged
               rather than completely forbidden in open interchange.  See
               "Noncharacter code points" in perlunicode.

               Use "isUTF8_CHAR" to check for Perl's extended UTF-8; and
               "isUTF8_CHAR_flags" for a more customized definition.

               Use "is_c9strict_utf8_string", "is_c9strict_utf8_string_loc",
               and "is_c9strict_utf8_string_loclen" to check entire strings.

                       STRLEN  isC9_STRICT_UTF8_CHAR(const U8 *s, const U8 *e)

       is_invariant_string
               This is a somewhat misleadingly-named synonym for
               "is_utf8_invariant_string".  "is_utf8_invariant_string" is
               preferred, as it indicates under what conditions the string is
               invariant.

                       bool    is_invariant_string(const U8* const s,
                                                   STRLEN len)

       isSTRICT_UTF8_CHAR
               Evaluates to non-zero if the first few bytes of the string
               starting at "s" and looking no further than "e-1" are well-
               formed UTF-8 that represents some Unicode code point completely
               acceptable for open interchange between all applications;
               otherwise it evaluates to 0.  If non-zero, the value gives how
               many bytes starting at "s" comprise the code point's
               representation.  Any bytes remaining before "e", but beyond the
               ones needed to form the first code point in "s", are not
               examined.

               The largest acceptable code point is the Unicode maximum
               0x10FFFF, and must not be a surrogate nor a non-character code
               point.  Thus this excludes any code point from Perl's extended
               UTF-8.

               This is used to efficiently decide if the next few bytes in "s"
               is legal Unicode-acceptable UTF-8 for a single character.

               Use "isC9_STRICT_UTF8_CHAR" to use the Unicode Corrigendum #9
               <http://www.unicode.org/versions/corrigendum9.html> definition
               of allowable code points; "isUTF8_CHAR" to check for Perl's
               extended UTF-8; and "isUTF8_CHAR_flags" for a more customized
               definition.

               Use "is_strict_utf8_string", "is_strict_utf8_string_loc", and
               "is_strict_utf8_string_loclen" to check entire strings.

                       Size_t  isSTRICT_UTF8_CHAR(const U8 * const s0,
                                                  const U8 * const e)

       is_strict_utf8_string
               Returns TRUE if the first "len" bytes of string "s" form a
               valid UTF-8-encoded string that is fully interchangeable by any
               application using Unicode rules; otherwise it returns FALSE.
               If "len" is 0, it will be calculated using strlen(s) (which
               means if you use this option, that "s" can't have embedded
               "NUL" characters and has to have a terminating "NUL" byte).
               Note that all characters being ASCII constitute 'a valid UTF-8
               string'.

               This function returns FALSE for strings containing any code
               points above the Unicode max of 0x10FFFF, surrogate code
               points, or non-character code points.

               See also "is_utf8_invariant_string",
               "is_utf8_invariant_string_loc", "is_utf8_string",
               "is_utf8_string_flags", "is_utf8_string_loc",
               "is_utf8_string_loc_flags", "is_utf8_string_loclen",
               "is_utf8_string_loclen_flags", "is_utf8_fixed_width_buf_flags",
               "is_utf8_fixed_width_buf_loc_flags",
               "is_utf8_fixed_width_buf_loclen_flags",
               "is_strict_utf8_string_loc", "is_strict_utf8_string_loclen",
               "is_c9strict_utf8_string", "is_c9strict_utf8_string_loc", and
               "is_c9strict_utf8_string_loclen".

                       bool    is_strict_utf8_string(const U8 *s, STRLEN len)

       is_strict_utf8_string_loc
               Like "is_strict_utf8_string" but stores the location of the
               failure (in the case of "utf8ness failure") or the location
               "s"+"len" (in the case of "utf8ness success") in the "ep"
               pointer.

               See also "is_strict_utf8_string_loclen".

                       bool    is_strict_utf8_string_loc(const U8 *s,
                                                         STRLEN len,
                                                         const U8 **ep)

       is_strict_utf8_string_loclen
               Like "is_strict_utf8_string" but stores the location of the
               failure (in the case of "utf8ness failure") or the location
               "s"+"len" (in the case of "utf8ness success") in the "ep"
               pointer, and the number of UTF-8 encoded characters in the "el"
               pointer.

               See also "is_strict_utf8_string_loc".

                       bool    is_strict_utf8_string_loclen(const U8 *s,
                                                            STRLEN len,
                                                            const U8 **ep,
                                                            STRLEN *el)

       is_utf8_fixed_width_buf_flags
               Returns TRUE if the fixed-width buffer starting at "s" with
               length "len" is entirely valid UTF-8, subject to the
               restrictions given by "flags"; otherwise it returns FALSE.

               If "flags" is 0, any well-formed UTF-8, as extended by Perl, is
               accepted without restriction.  If the final few bytes of the
               buffer do not form a complete code point, this will return TRUE
               anyway, provided that "is_utf8_valid_partial_char_flags"
               returns TRUE for them.

               If "flags" in non-zero, it can be any combination of the
               "UTF8_DISALLOW_foo" flags accepted by "utf8n_to_uvchr", and
               with the same meanings.

               This function differs from "is_utf8_string_flags" only in that
               the latter returns FALSE if the final few bytes of the string
               don't form a complete code point.

                       bool    is_utf8_fixed_width_buf_flags(
                                   const U8 * const s, STRLEN len,
                                   const U32 flags
                               )

       is_utf8_fixed_width_buf_loclen_flags
               Like "is_utf8_fixed_width_buf_loc_flags" but stores the number
               of complete, valid characters found in the "el" pointer.

                       bool    is_utf8_fixed_width_buf_loclen_flags(
                                   const U8 * const s, STRLEN len,
                                   const U8 **ep, STRLEN *el, const U32 flags
                               )

       is_utf8_fixed_width_buf_loc_flags
               Like "is_utf8_fixed_width_buf_flags" but stores the location of
               the failure in the "ep" pointer.  If the function returns TRUE,
               *ep will point to the beginning of any partial character at the
               end of the buffer; if there is no partial character *ep will
               contain "s"+"len".

               See also "is_utf8_fixed_width_buf_loclen_flags".

                       bool    is_utf8_fixed_width_buf_loc_flags(
                                   const U8 * const s, STRLEN len,
                                   const U8 **ep, const U32 flags
                               )

       is_utf8_invariant_string
               Returns TRUE if the first "len" bytes of the string "s" are the
               same regardless of the UTF-8 encoding of the string (or UTF-
               EBCDIC encoding on EBCDIC machines); otherwise it returns
               FALSE.  That is, it returns TRUE if they are UTF-8 invariant.
               On ASCII-ish machines, all the ASCII characters and only the
               ASCII characters fit this definition.  On EBCDIC machines, the
               ASCII-range characters are invariant, but so also are the C1
               controls.

               If "len" is 0, it will be calculated using strlen(s), (which
               means if you use this option, that "s" can't have embedded
               "NUL" characters and has to have a terminating "NUL" byte).

               See also "is_utf8_string", "is_utf8_string_flags",
               "is_utf8_string_loc", "is_utf8_string_loc_flags",
               "is_utf8_string_loclen", "is_utf8_string_loclen_flags",
               "is_utf8_fixed_width_buf_flags",
               "is_utf8_fixed_width_buf_loc_flags",
               "is_utf8_fixed_width_buf_loclen_flags",
               "is_strict_utf8_string", "is_strict_utf8_string_loc",
               "is_strict_utf8_string_loclen", "is_c9strict_utf8_string",
               "is_c9strict_utf8_string_loc", and
               "is_c9strict_utf8_string_loclen".

                       bool    is_utf8_invariant_string(const U8* const s,
                                                        STRLEN len)

       is_utf8_invariant_string_loc
               Like "is_utf8_invariant_string" but upon failure, stores the
               location of the first UTF-8 variant character in the "ep"
               pointer; if all characters are UTF-8 invariant, this function
               does not change the contents of *ep.

                       bool    is_utf8_invariant_string_loc(const U8* const s,
                                                            STRLEN len,
                                                            const U8 ** ep)

       is_utf8_string
               Returns TRUE if the first "len" bytes of string "s" form a
               valid Perl-extended-UTF-8 string; returns FALSE otherwise.  If
               "len" is 0, it will be calculated using strlen(s) (which means
               if you use this option, that "s" can't have embedded "NUL"
               characters and has to have a terminating "NUL" byte).  Note
               that all characters being ASCII constitute 'a valid UTF-8
               string'.

               This function considers Perl's extended UTF-8 to be valid.
               That means that code points above Unicode, surrogates, and non-
               character code points are considered valid by this function.
               Use "is_strict_utf8_string", "is_c9strict_utf8_string", or
               "is_utf8_string_flags" to restrict what code points are
               considered valid.

               See also "is_utf8_invariant_string",
               "is_utf8_invariant_string_loc", "is_utf8_string_loc",
               "is_utf8_string_loclen", "is_utf8_fixed_width_buf_flags",
               "is_utf8_fixed_width_buf_loc_flags",
               "is_utf8_fixed_width_buf_loclen_flags",

                       bool    is_utf8_string(const U8 *s, STRLEN len)

       is_utf8_string_flags
               Returns TRUE if the first "len" bytes of string "s" form a
               valid UTF-8 string, subject to the restrictions imposed by
               "flags"; returns FALSE otherwise.  If "len" is 0, it will be
               calculated using strlen(s) (which means if you use this option,
               that "s" can't have embedded "NUL" characters and has to have a
               terminating "NUL" byte).  Note that all characters being ASCII
               constitute 'a valid UTF-8 string'.

               If "flags" is 0, this gives the same results as
               "is_utf8_string"; if "flags" is
               "UTF8_DISALLOW_ILLEGAL_INTERCHANGE", this gives the same
               results as "is_strict_utf8_string"; and if "flags" is
               "UTF8_DISALLOW_ILLEGAL_C9_INTERCHANGE", this gives the same
               results as "is_c9strict_utf8_string".  Otherwise "flags" may be
               any combination of the "UTF8_DISALLOW_foo" flags understood by
               "utf8n_to_uvchr", with the same meanings.

               See also "is_utf8_invariant_string",
               "is_utf8_invariant_string_loc", "is_utf8_string",
               "is_utf8_string_loc", "is_utf8_string_loc_flags",
               "is_utf8_string_loclen", "is_utf8_string_loclen_flags",
               "is_utf8_fixed_width_buf_flags",
               "is_utf8_fixed_width_buf_loc_flags",
               "is_utf8_fixed_width_buf_loclen_flags",
               "is_strict_utf8_string", "is_strict_utf8_string_loc",
               "is_strict_utf8_string_loclen", "is_c9strict_utf8_string",
               "is_c9strict_utf8_string_loc", and
               "is_c9strict_utf8_string_loclen".

                       bool    is_utf8_string_flags(const U8 *s, STRLEN len,
                                                    const U32 flags)

       is_utf8_string_loc
               Like "is_utf8_string" but stores the location of the failure
               (in the case of "utf8ness failure") or the location "s"+"len"
               (in the case of "utf8ness success") in the "ep" pointer.

               See also "is_utf8_string_loclen".

                       bool    is_utf8_string_loc(const U8 *s,
                                                  const STRLEN len,
                                                  const U8 **ep)

       is_utf8_string_loclen
               Like "is_utf8_string" but stores the location of the failure
               (in the case of "utf8ness failure") or the location "s"+"len"
               (in the case of "utf8ness success") in the "ep" pointer, and
               the number of UTF-8 encoded characters in the "el" pointer.

               See also "is_utf8_string_loc".

                       bool    is_utf8_string_loclen(const U8 *s, STRLEN len,
                                                     const U8 **ep, STRLEN *el)

       is_utf8_string_loclen_flags
               Like "is_utf8_string_flags" but stores the location of the
               failure (in the case of "utf8ness failure") or the location
               "s"+"len" (in the case of "utf8ness success") in the "ep"
               pointer, and the number of UTF-8 encoded characters in the "el"
               pointer.

               See also "is_utf8_string_loc_flags".

                       bool    is_utf8_string_loclen_flags(const U8 *s,
                                                           STRLEN len,
                                                           const U8 **ep,
                                                           STRLEN *el,
                                                           const U32 flags)

       is_utf8_string_loc_flags
               Like "is_utf8_string_flags" but stores the location of the
               failure (in the case of "utf8ness failure") or the location
               "s"+"len" (in the case of "utf8ness success") in the "ep"
               pointer.

               See also "is_utf8_string_loclen_flags".

                       bool    is_utf8_string_loc_flags(const U8 *s,
                                                        STRLEN len,
                                                        const U8 **ep,
                                                        const U32 flags)

       is_utf8_valid_partial_char
               Returns 0 if the sequence of bytes starting at "s" and looking
               no further than "e-1" is the UTF-8 encoding, as extended by
               Perl, for one or more code points.  Otherwise, it returns 1 if
               there exists at least one non-empty sequence of bytes that when
               appended to sequence "s", starting at position "e" causes the
               entire sequence to be the well-formed UTF-8 of some code point;
               otherwise returns 0.

               In other words this returns TRUE if "s" points to a partial
               UTF-8-encoded code point.

               This is useful when a fixed-length buffer is being tested for
               being well-formed UTF-8, but the final few bytes in it don't
               comprise a full character; that is, it is split somewhere in
               the middle of the final code point's UTF-8 representation.
               (Presumably when the buffer is refreshed with the next chunk of
               data, the new first bytes will complete the partial code
               point.)   This function is used to verify that the final bytes
               in the current buffer are in fact the legal beginning of some
               code point, so that if they aren't, the failure can be
               signalled without having to wait for the next read.

                       bool    is_utf8_valid_partial_char(const U8 * const s,
                                                          const U8 * const e)

       is_utf8_valid_partial_char_flags
               Like "is_utf8_valid_partial_char", it returns a boolean giving
               whether or not the input is a valid UTF-8 encoded partial
               character, but it takes an extra parameter, "flags", which can
               further restrict which code points are considered valid.

               If "flags" is 0, this behaves identically to
               "is_utf8_valid_partial_char".  Otherwise "flags" can be any
               combination of the "UTF8_DISALLOW_foo" flags accepted by
               "utf8n_to_uvchr".  If there is any sequence of bytes that can
               complete the input partial character in such a way that a non-
               prohibited character is formed, the function returns TRUE;
               otherwise FALSE.  Non character code points cannot be
               determined based on partial character input.  But many  of the
               other possible excluded types can be determined from just the
               first one or two bytes.

                       bool    is_utf8_valid_partial_char_flags(
                                   const U8 * const s, const U8 * const e,
                                   const U32 flags
                               )

       isUTF8_CHAR
               Evaluates to non-zero if the first few bytes of the string
               starting at "s" and looking no further than "e-1" are well-
               formed UTF-8, as extended by Perl, that represents some code
               point; otherwise it evaluates to 0.  If non-zero, the value
               gives how many bytes starting at "s" comprise the code point's
               representation.  Any bytes remaining before "e", but beyond the
               ones needed to form the first code point in "s", are not
               examined.

               The code point can be any that will fit in an IV on this
               machine, using Perl's extension to official UTF-8 to represent
               those higher than the Unicode maximum of 0x10FFFF.  That means
               that this macro is used to efficiently decide if the next few
               bytes in "s" is legal UTF-8 for a single character.

               Use "isSTRICT_UTF8_CHAR" to restrict the acceptable code points
               to those defined by Unicode to be fully interchangeable across
               applications; "isC9_STRICT_UTF8_CHAR" to use the Unicode
               Corrigendum #9
               <http://www.unicode.org/versions/corrigendum9.html> definition
               of allowable code points; and "isUTF8_CHAR_flags" for a more
               customized definition.

               Use "is_utf8_string", "is_utf8_string_loc", and
               "is_utf8_string_loclen" to check entire strings.

               Note also that a UTF-8 "invariant" character (i.e. ASCII on
               non-EBCDIC machines) is a valid UTF-8 character.

                       STRLEN  isUTF8_CHAR(const U8 *s, const U8 *e)

       isUTF8_CHAR_flags
               Evaluates to non-zero if the first few bytes of the string
               starting at "s" and looking no further than "e-1" are well-
               formed UTF-8, as extended by Perl, that represents some code
               point, subject to the restrictions given by "flags"; otherwise
               it evaluates to 0.  If non-zero, the value gives how many bytes
               starting at "s" comprise the code point's representation.  Any
               bytes remaining before "e", but beyond the ones needed to form
               the first code point in "s", are not examined.

               If "flags" is 0, this gives the same results as "isUTF8_CHAR";
               if "flags" is "UTF8_DISALLOW_ILLEGAL_INTERCHANGE", this gives
               the same results as "isSTRICT_UTF8_CHAR"; and if "flags" is
               "UTF8_DISALLOW_ILLEGAL_C9_INTERCHANGE", this gives the same
               results as "isC9_STRICT_UTF8_CHAR".  Otherwise "flags" may be
               any combination of the "UTF8_DISALLOW_foo" flags understood by
               "utf8n_to_uvchr", with the same meanings.

               The three alternative macros are for the most commonly needed
               validations; they are likely to run somewhat faster than this
               more general one, as they can be inlined into your code.

               Use "is_utf8_string_flags", "is_utf8_string_loc_flags", and
               "is_utf8_string_loclen_flags" to check entire strings.

                       STRLEN  isUTF8_CHAR_flags(const U8 *s, const U8 *e,
                                                  const U32 flags)

       pv_uni_display
               Build to the scalar "dsv" a displayable version of the string
               "spv", length "len", the displayable version being at most
               "pvlim" bytes long (if longer, the rest is truncated and "..."
               will be appended).

               The "flags" argument can have "UNI_DISPLAY_ISPRINT" set to
               display "isPRINT()"able characters as themselves,
               "UNI_DISPLAY_BACKSLASH" to display the "\\[nrfta\\]" as the
               backslashed versions (like "\n") ("UNI_DISPLAY_BACKSLASH" is
               preferred over "UNI_DISPLAY_ISPRINT" for "\\").
               "UNI_DISPLAY_QQ" (and its alias "UNI_DISPLAY_REGEX") have both
               "UNI_DISPLAY_BACKSLASH" and "UNI_DISPLAY_ISPRINT" turned on.

               The pointer to the PV of the "dsv" is returned.

               See also "sv_uni_display".

                       char*   pv_uni_display(SV *dsv, const U8 *spv,
                                              STRLEN len, STRLEN pvlim,
                                              UV flags)

       REPLACEMENT_CHARACTER_UTF8
               This is a macro that evaluates to a string constant of the
               UTF-8 bytes that define the Unicode REPLACEMENT CHARACTER
               (U+FFFD) for the platform that perl is compiled on.  This
               allows code to use a mnemonic for this character that works on
               both ASCII and EBCDIC platforms.
               "sizeof(REPLACEMENT_CHARACTER_UTF8)-1" can be used to get its
               length in bytes.

       sv_cat_decode
               "encoding" is assumed to be an "Encode" object, the PV of "ssv"
               is assumed to be octets in that encoding and decoding the input
               starts from the position which "(PV+*offset)" pointed to.
               "dsv" will be concatenated with the decoded UTF-8 string from
               "ssv".  Decoding will terminate when the string "tstr" appears
               in decoding output or the input ends on the PV of "ssv".  The
               value which "offset" points will be modified to the last input
               position on "ssv".

               Returns TRUE if the terminator was found, else returns FALSE.

                       bool    sv_cat_decode(SV* dsv, SV *encoding, SV *ssv,
                                             int *offset, char* tstr, int tlen)

       sv_recode_to_utf8
               "encoding" is assumed to be an "Encode" object, on entry the PV
               of "sv" is assumed to be octets in that encoding, and "sv" will
               be converted into Unicode (and UTF-8).

               If "sv" already is UTF-8 (or if it is not "POK"), or if
               "encoding" is not a reference, nothing is done to "sv".  If
               "encoding" is not an "Encode::XS" Encoding object, bad things
               will happen.  (See cpan/Encode/encoding.pm and Encode.)

               The PV of "sv" is returned.

                       char*   sv_recode_to_utf8(SV* sv, SV *encoding)

       sv_uni_display
               Build to the scalar "dsv" a displayable version of the scalar
               "sv", the displayable version being at most "pvlim" bytes long
               (if longer, the rest is truncated and "..." will be appended).

               The "flags" argument is as in "pv_uni_display"().

               The pointer to the PV of the "dsv" is returned.

                       char*   sv_uni_display(SV *dsv, SV *ssv, STRLEN pvlim,
                                              UV flags)

       to_utf8_fold
               DEPRECATED!  It is planned to remove this function from a
               future release of Perl.  Do not use it for new code; remove it
               from existing code.

               Instead use "toFOLD_utf8_safe".

                       UV      to_utf8_fold(const U8 *p, U8* ustrp,
                                            STRLEN *lenp)

       to_utf8_lower
               DEPRECATED!  It is planned to remove this function from a
               future release of Perl.  Do not use it for new code; remove it
               from existing code.

               Instead use "toLOWER_utf8_safe".

                       UV      to_utf8_lower(const U8 *p, U8* ustrp,
                                             STRLEN *lenp)

       to_utf8_title
               DEPRECATED!  It is planned to remove this function from a
               future release of Perl.  Do not use it for new code; remove it
               from existing code.

               Instead use "toTITLE_utf8_safe".

                       UV      to_utf8_title(const U8 *p, U8* ustrp,
                                             STRLEN *lenp)

       to_utf8_upper
               DEPRECATED!  It is planned to remove this function from a
               future release of Perl.  Do not use it for new code; remove it
               from existing code.

               Instead use "toUPPER_utf8_safe".

                       UV      to_utf8_upper(const U8 *p, U8* ustrp,
                                             STRLEN *lenp)

       utf8n_to_uvchr
               THIS FUNCTION SHOULD BE USED IN ONLY VERY SPECIALIZED
               CIRCUMSTANCES.  Most code should use "utf8_to_uvchr_buf"()
               rather than call this directly.

               Bottom level UTF-8 decode routine.  Returns the native code
               point value of the first character in the string "s", which is
               assumed to be in UTF-8 (or UTF-EBCDIC) encoding, and no longer
               than "curlen" bytes; *retlen (if "retlen" isn't NULL) will be
               set to the length, in bytes, of that character.

               The value of "flags" determines the behavior when "s" does not
               point to a well-formed UTF-8 character.  If "flags" is 0,
               encountering a malformation causes zero to be returned and
               *retlen is set so that ("s"+*retlen) is the next possible
               position in "s" that could begin a non-malformed character.
               Also, if UTF-8 warnings haven't been lexically disabled, a
               warning is raised.  Some UTF-8 input sequences may contain
               multiple malformations.  This function tries to find every
               possible one in each call, so multiple warnings can be raised
               for the same sequence.

               Various ALLOW flags can be set in "flags" to allow (and not
               warn on) individual types of malformations, such as the
               sequence being overlong (that is, when there is a shorter
               sequence that can express the same code point; overlong
               sequences are expressly forbidden in the UTF-8 standard due to
               potential security issues).  Another malformation example is
               the first byte of a character not being a legal first byte.
               See utf8.h for the list of such flags.  Even if allowed, this
               function generally returns the Unicode REPLACEMENT CHARACTER
               when it encounters a malformation.  There are flags in utf8.h
               to override this behavior for the overlong malformations, but
               don't do that except for very specialized purposes.

               The "UTF8_CHECK_ONLY" flag overrides the behavior when a non-
               allowed (by other flags) malformation is found.  If this flag
               is set, the routine assumes that the caller will raise a
               warning, and this function will silently just set "retlen" to
               "-1" (cast to "STRLEN") and return zero.

               Note that this API requires disambiguation between successful
               decoding a "NUL" character, and an error return (unless the
               "UTF8_CHECK_ONLY" flag is set), as in both cases, 0 is
               returned, and, depending on the malformation, "retlen" may be
               set to 1.  To disambiguate, upon a zero return, see if the
               first byte of "s" is 0 as well.  If so, the input was a "NUL";
               if not, the input had an error.  Or you can use
               "utf8n_to_uvchr_error".

               Certain code points are considered problematic.  These are
               Unicode surrogates, Unicode non-characters, and code points
               above the Unicode maximum of 0x10FFFF.  By default these are
               considered regular code points, but certain situations warrant
               special handling for them, which can be specified using the
               "flags" parameter.  If "flags" contains
               "UTF8_DISALLOW_ILLEGAL_INTERCHANGE", all three classes are
               treated as malformations and handled as such.  The flags
               "UTF8_DISALLOW_SURROGATE", "UTF8_DISALLOW_NONCHAR", and
               "UTF8_DISALLOW_SUPER" (meaning above the legal Unicode maximum)
               can be set to disallow these categories individually.
               "UTF8_DISALLOW_ILLEGAL_INTERCHANGE" restricts the allowed
               inputs to the strict UTF-8 traditionally defined by Unicode.
               Use "UTF8_DISALLOW_ILLEGAL_C9_INTERCHANGE" to use the
               strictness definition given by Unicode Corrigendum #9
               <http://www.unicode.org/versions/corrigendum9.html>.  The
               difference between traditional strictness and C9 strictness is
               that the latter does not forbid non-character code points.
               (They are still discouraged, however.)  For more discussion see
               "Noncharacter code points" in perlunicode.

               The flags "UTF8_WARN_ILLEGAL_INTERCHANGE",
               "UTF8_WARN_ILLEGAL_C9_INTERCHANGE", "UTF8_WARN_SURROGATE",
               "UTF8_WARN_NONCHAR", and "UTF8_WARN_SUPER" will cause warning
               messages to be raised for their respective categories, but
               otherwise the code points are considered valid (not
               malformations).  To get a category to both be treated as a
               malformation and raise a warning, specify both the WARN and
               DISALLOW flags.  (But note that warnings are not raised if
               lexically disabled nor if "UTF8_CHECK_ONLY" is also specified.)

               Extremely high code points were never specified in any
               standard, and require an extension to UTF-8 to express, which
               Perl does.  It is likely that programs written in something
               other than Perl would not be able to read files that contain
               these; nor would Perl understand files written by something
               that uses a different extension.  For these reasons, there is a
               separate set of flags that can warn and/or disallow these
               extremely high code points, even if other above-Unicode ones
               are accepted.  They are the "UTF8_WARN_PERL_EXTENDED" and
               "UTF8_DISALLOW_PERL_EXTENDED" flags.  For more information see
               ""UTF8_GOT_PERL_EXTENDED"".  Of course "UTF8_DISALLOW_SUPER"
               will treat all above-Unicode code points, including these, as
               malformations.  (Note that the Unicode standard considers
               anything above 0x10FFFF to be illegal, but there are standards
               predating it that allow up to 0x7FFF_FFFF (2**31 -1))

               A somewhat misleadingly named synonym for
               "UTF8_WARN_PERL_EXTENDED" is retained for backward
               compatibility: "UTF8_WARN_ABOVE_31_BIT".  Similarly,
               "UTF8_DISALLOW_ABOVE_31_BIT" is usable instead of the more
               accurately named "UTF8_DISALLOW_PERL_EXTENDED".  The names are
               misleading because these flags can apply to code points that
               actually do fit in 31 bits.  This happens on EBCDIC platforms,
               and sometimes when the overlong malformation is also present.
               The new names accurately describe the situation in all cases.

               All other code points corresponding to Unicode characters,
               including private use and those yet to be assigned, are never
               considered malformed and never warn.

                       UV      utf8n_to_uvchr(const U8 *s, STRLEN curlen,
                                              STRLEN *retlen, const U32 flags)

       utf8n_to_uvchr_error
               THIS FUNCTION SHOULD BE USED IN ONLY VERY SPECIALIZED
               CIRCUMSTANCES.  Most code should use "utf8_to_uvchr_buf"()
               rather than call this directly.

               This function is for code that needs to know what the precise
               malformation(s) are when an error is found.  If you also need
               to know the generated warning messages, use
               "utf8n_to_uvchr_msgs"() instead.

               It is like "utf8n_to_uvchr" but it takes an extra parameter
               placed after all the others, "errors".  If this parameter is 0,
               this function behaves identically to "utf8n_to_uvchr".
               Otherwise, "errors" should be a pointer to a "U32" variable,
               which this function sets to indicate any errors found.  Upon
               return, if *errors is 0, there were no errors found.
               Otherwise, *errors is the bit-wise "OR" of the bits described
               in the list below.  Some of these bits will be set if a
               malformation is found, even if the input "flags" parameter
               indicates that the given malformation is allowed; those
               exceptions are noted:

               "UTF8_GOT_PERL_EXTENDED"
                   The input sequence is not standard UTF-8, but a Perl
                   extension.  This bit is set only if the input "flags"
                   parameter contains either the "UTF8_DISALLOW_PERL_EXTENDED"
                   or the "UTF8_WARN_PERL_EXTENDED" flags.

                   Code points above 0x7FFF_FFFF (2**31 - 1) were never
                   specified in any standard, and so some extension must be
                   used to express them.  Perl uses a natural extension to
                   UTF-8 to represent the ones up to 2**36-1, and invented a
                   further extension to represent even higher ones, so that
                   any code point that fits in a 64-bit word can be
                   represented.  Text using these extensions is not likely to
                   be portable to non-Perl code.  We lump both of these
                   extensions together and refer to them as Perl extended
                   UTF-8.  There exist other extensions that people have
                   invented, incompatible with Perl's.

                   On EBCDIC platforms starting in Perl v5.24, the Perl
                   extension for representing extremely high code points kicks
                   in at 0x3FFF_FFFF (2**30 -1), which is lower than on ASCII.
                   Prior to that, code points 2**31 and higher were simply
                   unrepresentable, and a different, incompatible method was
                   used to represent code points between 2**30 and 2**31 - 1.

                   On both platforms, ASCII and EBCDIC,
                   "UTF8_GOT_PERL_EXTENDED" is set if Perl extended UTF-8 is
                   used.

                   In earlier Perls, this bit was named
                   "UTF8_GOT_ABOVE_31_BIT", which you still may use for
                   backward compatibility.  That name is misleading, as this
                   flag may be set when the code point actually does fit in 31
                   bits.  This happens on EBCDIC platforms, and sometimes when
                   the overlong malformation is also present.  The new name
                   accurately describes the situation in all cases.

               "UTF8_GOT_CONTINUATION"
                   The input sequence was malformed in that the first byte was
                   a a UTF-8 continuation byte.

               "UTF8_GOT_EMPTY"
                   The input "curlen" parameter was 0.

               "UTF8_GOT_LONG"
                   The input sequence was malformed in that there is some
                   other sequence that evaluates to the same code point, but
                   that sequence is shorter than this one.

                   Until Unicode 3.1, it was legal for programs to accept this
                   malformation, but it was discovered that this created
                   security issues.

               "UTF8_GOT_NONCHAR"
                   The code point represented by the input UTF-8 sequence is
                   for a Unicode non-character code point.  This bit is set
                   only if the input "flags" parameter contains either the
                   "UTF8_DISALLOW_NONCHAR" or the "UTF8_WARN_NONCHAR" flags.

               "UTF8_GOT_NON_CONTINUATION"
                   The input sequence was malformed in that a non-continuation
                   type byte was found in a position where only a continuation
                   type one should be.  See also ""UTF8_GOT_SHORT"".

               "UTF8_GOT_OVERFLOW"
                   The input sequence was malformed in that it is for a code
                   point that is not representable in the number of bits
                   available in an IV on the current platform.

               "UTF8_GOT_SHORT"
                   The input sequence was malformed in that "curlen" is
                   smaller than required for a complete sequence.  In other
                   words, the input is for a partial character sequence.

                   "UTF8_GOT_SHORT" and "UTF8_GOT_NON_CONTINUATION" both
                   indicate a too short sequence.  The difference is that
                   "UTF8_GOT_NON_CONTINUATION" indicates always that there is
                   an error, while "UTF8_GOT_SHORT" means that an incomplete
                   sequence was looked at.   If no other flags are present, it
                   means that the sequence was valid as far as it went.
                   Depending on the application, this could mean one of three
                   things:

                   o   The "curlen" length parameter passed in was too small,
                       and the function was prevented from examining all the
                       necessary bytes.

                   o   The buffer being looked at is based on reading data,
                       and the data received so far stopped in the middle of a
                       character, so that the next read will read the
                       remainder of this character.  (It is up to the caller
                       to deal with the split bytes somehow.)

                   o   This is a real error, and the partial sequence is all
                       we're going to get.

               "UTF8_GOT_SUPER"
                   The input sequence was malformed in that it is for a non-
                   Unicode code point; that is, one above the legal Unicode
                   maximum.  This bit is set only if the input "flags"
                   parameter contains either the "UTF8_DISALLOW_SUPER" or the
                   "UTF8_WARN_SUPER" flags.

               "UTF8_GOT_SURROGATE"
                   The input sequence was malformed in that it is for a
                   -Unicode UTF-16 surrogate code point.  This bit is set only
                   if the input "flags" parameter contains either the
                   "UTF8_DISALLOW_SURROGATE" or the "UTF8_WARN_SURROGATE"
                   flags.

               To do your own error handling, call this function with the
               "UTF8_CHECK_ONLY" flag to suppress any warnings, and then
               examine the *errors return.

                       UV      utf8n_to_uvchr_error(const U8 *s, STRLEN curlen,
                                                    STRLEN *retlen,
                                                    const U32 flags,
                                                    U32 * errors)

       utf8n_to_uvchr_msgs
               NOTE: this function is experimental and may change or be
               removed without notice.

               THIS FUNCTION SHOULD BE USED IN ONLY VERY SPECIALIZED
               CIRCUMSTANCES.  Most code should use "utf8_to_uvchr_buf"()
               rather than call this directly.

               This function is for code that needs to know what the precise
               malformation(s) are when an error is found, and wants the
               corresponding warning and/or error messages to be returned to
               the caller rather than be displayed.  All messages that would
               have been displayed if all lexcial warnings are enabled will be
               returned.

               It is just like "utf8n_to_uvchr_error" but it takes an extra
               parameter placed after all the others, "msgs".  If this
               parameter is 0, this function behaves identically to
               "utf8n_to_uvchr_error".  Otherwise, "msgs" should be a pointer
               to an "AV *" variable, in which this function creates a new AV
               to contain any appropriate messages.  The elements of the array
               are ordered so that the first message that would have been
               displayed is in the 0th element, and so on.  Each element is a
               hash with three key-value pairs, as follows:

               "text"
                   The text of the message as a "SVpv".

               "warn_categories"
                   The warning category (or categories) packed into a "SVuv".

               "flag"
                   A single flag bit associated with this message, in a
                   "SVuv".  The bit corresponds to some bit in the *errors
                   return value, such as "UTF8_GOT_LONG".

               It's important to note that specifying this parameter as non-
               null will cause any warnings this function would otherwise
               generate to be suppressed, and instead be placed in *msgs.  The
               caller can check the lexical warnings state (or not) when
               choosing what to do with the returned messages.

               If the flag "UTF8_CHECK_ONLY" is passed, no warnings are
               generated, and hence no AV is created.

               The caller, of course, is responsible for freeing any returned
               AV.

                       UV      utf8n_to_uvchr_msgs(const U8 *s, STRLEN curlen,
                                                   STRLEN *retlen,
                                                   const U32 flags,
                                                   U32 * errors, AV ** msgs)

       utf8n_to_uvuni
               Instead use "utf8_to_uvchr_buf", or rarely, "utf8n_to_uvchr".

               This function was useful for code that wanted to handle both
               EBCDIC and ASCII platforms with Unicode properties, but
               starting in Perl v5.20, the distinctions between the platforms
               have mostly been made invisible to most code, so this function
               is quite unlikely to be what you want.  If you do need this
               precise functionality, use instead
               "NATIVE_TO_UNI(utf8_to_uvchr_buf(...))"  or
               "NATIVE_TO_UNI(utf8n_to_uvchr(...))".

                       UV      utf8n_to_uvuni(const U8 *s, STRLEN curlen,
                                              STRLEN *retlen, U32 flags)

       UTF8SKIP
               returns the number of bytes in the UTF-8 encoded character
               whose first (perhaps only) byte is pointed to by "s".

                       STRLEN  UTF8SKIP(char* s)

       utf8_distance
               Returns the number of UTF-8 characters between the UTF-8
               pointers "a" and "b".

               WARNING: use only if you *know* that the pointers point inside
               the same UTF-8 buffer.

                       IV      utf8_distance(const U8 *a, const U8 *b)

       utf8_hop
               Return the UTF-8 pointer "s" displaced by "off" characters,
               either forward or backward.

               WARNING: do not use the following unless you *know* "off" is
               within the UTF-8 data pointed to by "s" *and* that on entry "s"
               is aligned on the first byte of character or just after the
               last byte of a character.

                       U8*     utf8_hop(const U8 *s, SSize_t off)

       utf8_hop_back
               Return the UTF-8 pointer "s" displaced by up to "off"
               characters, backward.

               "off" must be non-positive.

               "s" must be after or equal to "start".

               When moving backward it will not move before "start".

               Will not exceed this limit even if the string is not valid
               "UTF-8".

                       U8*     utf8_hop_back(const U8 *s, SSize_t off,
                                             const U8 *start)

       utf8_hop_forward
               Return the UTF-8 pointer "s" displaced by up to "off"
               characters, forward.

               "off" must be non-negative.

               "s" must be before or equal to "end".

               When moving forward it will not move beyond "end".

               Will not exceed this limit even if the string is not valid
               "UTF-8".

                       U8*     utf8_hop_forward(const U8 *s, SSize_t off,
                                                const U8 *end)

       utf8_hop_safe
               Return the UTF-8 pointer "s" displaced by up to "off"
               characters, either forward or backward.

               When moving backward it will not move before "start".

               When moving forward it will not move beyond "end".

               Will not exceed those limits even if the string is not valid
               "UTF-8".

                       U8*     utf8_hop_safe(const U8 *s, SSize_t off,
                                             const U8 *start, const U8 *end)

       UTF8_IS_INVARIANT
               Evaluates to 1 if the byte "c" represents the same character
               when encoded in UTF-8 as when not; otherwise evaluates to 0.
               UTF-8 invariant characters can be copied as-is when converting
               to/from UTF-8, saving time.

               In spite of the name, this macro gives the correct result if
               the input string from which "c" comes is not encoded in UTF-8.

               See "UVCHR_IS_INVARIANT" for checking if a UV is invariant.

                       bool    UTF8_IS_INVARIANT(char c)

       UTF8_IS_NONCHAR
               Evaluates to non-zero if the first few bytes of the string
               starting at "s" and looking no further than "e-1" are well-
               formed UTF-8 that represents one of the Unicode non-character
               code points; otherwise it evaluates to 0.  If non-zero, the
               value gives how many bytes starting at "s" comprise the code
               point's representation.

                       bool    UTF8_IS_NONCHAR(const U8 *s, const U8 *e)

       UTF8_IS_SUPER
               Recall that Perl recognizes an extension to UTF-8 that can
               encode code points larger than the ones defined by Unicode,
               which are 0..0x10FFFF.

               This macro evaluates to non-zero if the first few bytes of the
               string starting at "s" and looking no further than "e-1" are
               from this UTF-8 extension; otherwise it evaluates to 0.  If
               non-zero, the value gives how many bytes starting at "s"
               comprise the code point's representation.

               0 is returned if the bytes are not well-formed extended UTF-8,
               or if they represent a code point that cannot fit in a UV on
               the current platform.  Hence this macro can give different
               results when run on a 64-bit word machine than on one with a
               32-bit word size.

               Note that it is illegal to have code points that are larger
               than what can fit in an IV on the current machine.

                       bool    UTF8_IS_SUPER(const U8 *s, const U8 *e)

       UTF8_IS_SURROGATE
               Evaluates to non-zero if the first few bytes of the string
               starting at "s" and looking no further than "e-1" are well-
               formed UTF-8 that represents one of the Unicode surrogate code
               points; otherwise it evaluates to 0.  If non-zero, the value
               gives how many bytes starting at "s" comprise the code point's
               representation.

                       bool    UTF8_IS_SURROGATE(const U8 *s, const U8 *e)

       utf8_length
               Returns the number of characters in the sequence of
               UTF-8-encoded bytes starting at "s" and ending at the byte just
               before "e".  If <s> and <e> point to the same place, it returns
               0 with no warning raised.

               If "e < s" or if the scan would end up past "e", it raises a
               UTF8 warning and returns the number of valid characters.

                       STRLEN  utf8_length(const U8* s, const U8 *e)

       UTF8_SAFE_SKIP
               returns 0 if "s>=e"; otherwise returns the number of bytes in
               the UTF-8 encoded character whose first  byte is pointed to by
               "s".  But it never returns beyond "e".  On DEBUGGING builds, it
               asserts that "s<=e".

                       STRLEN  UTF8_SAFE_SKIP(char* s, char* e)

       utf8_to_bytes
               NOTE: this function is experimental and may change or be
               removed without notice.

               Converts a string "s" of length *lenp from UTF-8 into native
               byte encoding.  Unlike "bytes_to_utf8", this over-writes the
               original string, and updates *lenp to contain the new length.
               Returns zero on failure (leaving "s" unchanged) setting *lenp
               to -1.

               Upon successful return, the number of variants in the string
               can be computed by having saved the value of *lenp before the
               call, and subtracting the after-call value of *lenp from it.

               If you need a copy of the string, see "bytes_from_utf8".

                       U8*     utf8_to_bytes(U8 *s, STRLEN *lenp)

       utf8_to_uvchr
               DEPRECATED!  It is planned to remove this function from a
               future release of Perl.  Do not use it for new code; remove it
               from existing code.

               Returns the native code point of the first character in the
               string "s" which is assumed to be in UTF-8 encoding; "retlen"
               will be set to the length, in bytes, of that character.

               Some, but not all, UTF-8 malformations are detected, and in
               fact, some malformed input could cause reading beyond the end
               of the input buffer, which is why this function is deprecated.
               Use "utf8_to_uvchr_buf" instead.

               If "s" points to one of the detected malformations, and UTF8
               warnings are enabled, zero is returned and *retlen is set (if
               "retlen" isn't "NULL") to -1.  If those warnings are off, the
               computed value if well-defined (or the Unicode REPLACEMENT
               CHARACTER, if not) is silently returned, and *retlen is set (if
               "retlen" isn't NULL) so that ("s"+*retlen) is the next possible
               position in "s" that could begin a non-malformed character.
               See "utf8n_to_uvchr" for details on when the REPLACEMENT
               CHARACTER is returned.

                       UV      utf8_to_uvchr(const U8 *s, STRLEN *retlen)

       utf8_to_uvchr_buf
               Returns the native code point of the first character in the
               string "s" which is assumed to be in UTF-8 encoding; "send"
               points to 1 beyond the end of "s".  *retlen will be set to the
               length, in bytes, of that character.

               If "s" does not point to a well-formed UTF-8 character and UTF8
               warnings are enabled, zero is returned and *retlen is set (if
               "retlen" isn't "NULL") to -1.  If those warnings are off, the
               computed value, if well-defined (or the Unicode REPLACEMENT
               CHARACTER if not), is silently returned, and *retlen is set (if
               "retlen" isn't "NULL") so that ("s"+*retlen) is the next
               possible position in "s" that could begin a non-malformed
               character.  See "utf8n_to_uvchr" for details on when the
               REPLACEMENT CHARACTER is returned.

                       UV      utf8_to_uvchr_buf(const U8 *s, const U8 *send,
                                                 STRLEN *retlen)

       utf8_to_uvuni_buf
               DEPRECATED!  It is planned to remove this function from a
               future release of Perl.  Do not use it for new code; remove it
               from existing code.

               Only in very rare circumstances should code need to be dealing
               in Unicode (as opposed to native) code points.  In those few
               cases, use "NATIVE_TO_UNI(utf8_to_uvchr_buf(...))" instead.  If
               you are not absolutely sure this is one of those cases, then
               assume it isn't and use plain "utf8_to_uvchr_buf" instead.

               Returns the Unicode (not-native) code point of the first
               character in the string "s" which is assumed to be in UTF-8
               encoding; "send" points to 1 beyond the end of "s".  "retlen"
               will be set to the length, in bytes, of that character.

               If "s" does not point to a well-formed UTF-8 character and UTF8
               warnings are enabled, zero is returned and *retlen is set (if
               "retlen" isn't NULL) to -1.  If those warnings are off, the
               computed value if well-defined (or the Unicode REPLACEMENT
               CHARACTER, if not) is silently returned, and *retlen is set (if
               "retlen" isn't NULL) so that ("s"+*retlen) is the next possible
               position in "s" that could begin a non-malformed character.
               See "utf8n_to_uvchr" for details on when the REPLACEMENT
               CHARACTER is returned.

                       UV      utf8_to_uvuni_buf(const U8 *s, const U8 *send,
                                                 STRLEN *retlen)

       UVCHR_IS_INVARIANT
               Evaluates to 1 if the representation of code point "cp" is the
               same whether or not it is encoded in UTF-8; otherwise evaluates
               to 0.  UTF-8 invariant characters can be copied as-is when
               converting to/from UTF-8, saving time.  "cp" is Unicode if
               above 255; otherwise is platform-native.

                       bool    UVCHR_IS_INVARIANT(UV cp)

       UVCHR_SKIP
               returns the number of bytes required to represent the code
               point "cp" when encoded as UTF-8.  "cp" is a native (ASCII or
               EBCDIC) code point if less than 255; a Unicode code point
               otherwise.

                       STRLEN  UVCHR_SKIP(UV cp)

       uvchr_to_utf8
               Adds the UTF-8 representation of the native code point "uv" to
               the end of the string "d"; "d" should have at least
               "UVCHR_SKIP(uv)+1" (up to "UTF8_MAXBYTES+1") free bytes
               available.  The return value is the pointer to the byte after
               the end of the new character.  In other words,

                   d = uvchr_to_utf8(d, uv);

               is the recommended wide native character-aware way of saying

                   *(d++) = uv;

               This function accepts any code point from 0.."IV_MAX" as input.
               "IV_MAX" is typically 0x7FFF_FFFF in a 32-bit word.

               It is possible to forbid or warn on non-Unicode code points, or
               those that may be problematic by using "uvchr_to_utf8_flags".

                       U8*     uvchr_to_utf8(U8 *d, UV uv)

       uvchr_to_utf8_flags
               Adds the UTF-8 representation of the native code point "uv" to
               the end of the string "d"; "d" should have at least
               "UVCHR_SKIP(uv)+1" (up to "UTF8_MAXBYTES+1") free bytes
               available.  The return value is the pointer to the byte after
               the end of the new character.  In other words,

                   d = uvchr_to_utf8_flags(d, uv, flags);

               or, in most cases,

                   d = uvchr_to_utf8_flags(d, uv, 0);

               This is the Unicode-aware way of saying

                   *(d++) = uv;

               If "flags" is 0, this function accepts any code point from
               0.."IV_MAX" as input.  "IV_MAX" is typically 0x7FFF_FFFF in a
               32-bit word.

               Specifying "flags" can further restrict what is allowed and not
               warned on, as follows:

               If "uv" is a Unicode surrogate code point and
               "UNICODE_WARN_SURROGATE" is set, the function will raise a
               warning, provided UTF8 warnings are enabled.  If instead
               "UNICODE_DISALLOW_SURROGATE" is set, the function will fail and
               return NULL.  If both flags are set, the function will both
               warn and return NULL.

               Similarly, the "UNICODE_WARN_NONCHAR" and
               "UNICODE_DISALLOW_NONCHAR" flags affect how the function
               handles a Unicode non-character.

               And likewise, the "UNICODE_WARN_SUPER" and
               "UNICODE_DISALLOW_SUPER" flags affect the handling of code
               points that are above the Unicode maximum of 0x10FFFF.
               Languages other than Perl may not be able to accept files that
               contain these.

               The flag "UNICODE_WARN_ILLEGAL_INTERCHANGE" selects all three
               of the above WARN flags; and
               "UNICODE_DISALLOW_ILLEGAL_INTERCHANGE" selects all three
               DISALLOW flags.  "UNICODE_DISALLOW_ILLEGAL_INTERCHANGE"
               restricts the allowed inputs to the strict UTF-8 traditionally
               defined by Unicode.  Similarly,
               "UNICODE_WARN_ILLEGAL_C9_INTERCHANGE" and
               "UNICODE_DISALLOW_ILLEGAL_C9_INTERCHANGE" are shortcuts to
               select the above-Unicode and surrogate flags, but not the non-
               character ones, as defined in Unicode Corrigendum #9
               <http://www.unicode.org/versions/corrigendum9.html>.  See
               "Noncharacter code points" in perlunicode.

               Extremely high code points were never specified in any
               standard, and require an extension to UTF-8 to express, which
               Perl does.  It is likely that programs written in something
               other than Perl would not be able to read files that contain
               these; nor would Perl understand files written by something
               that uses a different extension.  For these reasons, there is a
               separate set of flags that can warn and/or disallow these
               extremely high code points, even if other above-Unicode ones
               are accepted.  They are the "UNICODE_WARN_PERL_EXTENDED" and
               "UNICODE_DISALLOW_PERL_EXTENDED" flags.  For more information
               see ""UTF8_GOT_PERL_EXTENDED"".  Of course
               "UNICODE_DISALLOW_SUPER" will treat all above-Unicode code
               points, including these, as malformations.  (Note that the
               Unicode standard considers anything above 0x10FFFF to be
               illegal, but there are standards predating it that allow up to
               0x7FFF_FFFF (2**31 -1))

               A somewhat misleadingly named synonym for
               "UNICODE_WARN_PERL_EXTENDED" is retained for backward
               compatibility: "UNICODE_WARN_ABOVE_31_BIT".  Similarly,
               "UNICODE_DISALLOW_ABOVE_31_BIT" is usable instead of the more
               accurately named "UNICODE_DISALLOW_PERL_EXTENDED".  The names
               are misleading because on EBCDIC platforms,these flags can
               apply to code points that actually do fit in 31 bits.  The new
               names accurately describe the situation in all cases.

                       U8*     uvchr_to_utf8_flags(U8 *d, UV uv, UV flags)

       uvchr_to_utf8_flags_msgs
               NOTE: this function is experimental and may change or be
               removed without notice.

               THIS FUNCTION SHOULD BE USED IN ONLY VERY SPECIALIZED
               CIRCUMSTANCES.

               Most code should use ""uvchr_to_utf8_flags"()" rather than call
               this directly.

               This function is for code that wants any warning and/or error
               messages to be returned to the caller rather than be displayed.
               All messages that would have been displayed if all lexical
               warnings are enabled will be returned.

               It is just like "uvchr_to_utf8_flags" but it takes an extra
               parameter placed after all the others, "msgs".  If this
               parameter is 0, this function behaves identically to
               "uvchr_to_utf8_flags".  Otherwise, "msgs" should be a pointer
               to an "HV *" variable, in which this function creates a new HV
               to contain any appropriate messages.  The hash has three key-
               value pairs, as follows:

               "text"
                   The text of the message as a "SVpv".

               "warn_categories"
                   The warning category (or categories) packed into a "SVuv".

               "flag"
                   A single flag bit associated with this message, in a
                   "SVuv".  The bit corresponds to some bit in the *errors
                   return value, such as "UNICODE_GOT_SURROGATE".

               It's important to note that specifying this parameter as non-
               null will cause any warnings this function would otherwise
               generate to be suppressed, and instead be placed in *msgs.  The
               caller can check the lexical warnings state (or not) when
               choosing what to do with the returned messages.

               The caller, of course, is responsible for freeing any returned
               HV.

                       U8*     uvchr_to_utf8_flags_msgs(U8 *d, UV uv, UV flags,
                                                        HV ** msgs)

       uvoffuni_to_utf8_flags
               THIS FUNCTION SHOULD BE USED IN ONLY VERY SPECIALIZED
               CIRCUMSTANCES.  Instead, Almost all code should use
               "uvchr_to_utf8" or "uvchr_to_utf8_flags".

               This function is like them, but the input is a strict Unicode
               (as opposed to native) code point.  Only in very rare
               circumstances should code not be using the native code point.

               For details, see the description for "uvchr_to_utf8_flags".

                       U8*     uvoffuni_to_utf8_flags(U8 *d, UV uv,
                                                      const UV flags)

       uvuni_to_utf8_flags
               Instead you almost certainly want to use "uvchr_to_utf8" or
               "uvchr_to_utf8_flags".

               This function is a deprecated synonym for
               "uvoffuni_to_utf8_flags", which itself, while not deprecated,
               should be used only in isolated circumstances.  These functions
               were useful for code that wanted to handle both EBCDIC and
               ASCII platforms with Unicode properties, but starting in Perl
               v5.20, the distinctions between the platforms have mostly been
               made invisible to most code, so this function is quite unlikely
               to be what you want.

                       U8*     uvuni_to_utf8_flags(U8 *d, UV uv, UV flags)

       valid_utf8_to_uvchr
               Like "utf8_to_uvchr_buf", but should only be called when it is
               known that the next character in the input UTF-8 string "s" is
               well-formed (e.g., it passes "isUTF8_CHAR".  Surrogates, non-
               character code points, and non-Unicode code points are allowed.

                       UV      valid_utf8_to_uvchr(const U8 *s, STRLEN *retlen)

Variables created by "xsubpp" and "xsubpp" internal functions
       newXSproto
               Used by "xsubpp" to hook up XSUBs as Perl subs.  Adds Perl
               prototypes to the subs.

       XS_APIVERSION_BOOTCHECK
               Macro to verify that the perl api version an XS module has been
               compiled against matches the api version of the perl
               interpreter it's being loaded into.

                               XS_APIVERSION_BOOTCHECK;

       XS_VERSION
               The version identifier for an XS module.  This is usually
               handled automatically by "ExtUtils::MakeMaker".  See
               "XS_VERSION_BOOTCHECK".

       XS_VERSION_BOOTCHECK
               Macro to verify that a PM module's $VERSION variable matches
               the XS module's "XS_VERSION" variable.  This is usually handled
               automatically by "xsubpp".  See "The VERSIONCHECK: Keyword" in
               perlxs.

                               XS_VERSION_BOOTCHECK;

Warning and Dieing
       ckWARN  Returns a boolean as to whether or not warnings are enabled for
               the warning category "w".  If the category is by default
               enabled even if not within the scope of "usewarnings", instead
               use the "ckWARN_d" macro.

                       bool    ckWARN(U32 w)

       ckWARN2 Like "ckWARN", but takes two warnings categories as input, and
               returns TRUE if either is enabled.  If either category is by
               default enabled even if not within the scope of "usewarnings",
               instead use the "ckWARN2_d" macro.  The categories must be
               completely independent, one may not be subclassed from the
               other.

                       bool    ckWARN2(U32 w1, U32 w2)

       ckWARN3 Like "ckWARN2", but takes three warnings categories as input,
               and returns TRUE if any is enabled.  If any of the categories
               is by default enabled even if not within the scope of
               "usewarnings", instead use the "ckWARN3_d" macro.  The
               categories must be completely independent, one may not be
               subclassed from any other.

                       bool    ckWARN3(U32 w1, U32 w2, U32 w3)

       ckWARN4 Like "ckWARN3", but takes four warnings categories as input,
               and returns TRUE if any is enabled.  If any of the categories
               is by default enabled even if not within the scope of
               "usewarnings", instead use the "ckWARN4_d" macro.  The
               categories must be completely independent, one may not be
               subclassed from any other.

                       bool    ckWARN4(U32 w1, U32 w2, U32 w3, U32 w4)

       ckWARN_d
               Like "ckWARN", but for use if and only if the warning category
               is by default enabled even if not within the scope of
               "usewarnings".

                       bool    ckWARN_d(U32 w)

       ckWARN2_d
               Like "ckWARN2", but for use if and only if either warning
               category is by default enabled even if not within the scope of
               "usewarnings".

                       bool    ckWARN2_d(U32 w1, U32 w2)

       ckWARN3_d
               Like "ckWARN3", but for use if and only if any of the warning
               categories is by default enabled even if not within the scope
               of "usewarnings".

                       bool    ckWARN3_d(U32 w1, U32 w2, U32 w3)

       ckWARN4_d
               Like "ckWARN4", but for use if and only if any of the warning
               categories is by default enabled even if not within the scope
               of "usewarnings".

                       bool    ckWARN4_d(U32 w1, U32 w2, U32 w3, U32 w4)

       croak   This is an XS interface to Perl's "die" function.

               Take a sprintf-style format pattern and argument list.  These
               are used to generate a string message.  If the message does not
               end with a newline, then it will be extended with some
               indication of the current location in the code, as described
               for "mess_sv".

               The error message will be used as an exception, by default
               returning control to the nearest enclosing "eval", but subject
               to modification by a $SIG{__DIE__} handler.  In any case, the
               "croak" function never returns normally.

               For historical reasons, if "pat" is null then the contents of
               "ERRSV" ($@) will be used as an error message or object instead
               of building an error message from arguments.  If you want to
               throw a non-string object, or build an error message in an SV
               yourself, it is preferable to use the "croak_sv" function,
               which does not involve clobbering "ERRSV".

                       void    croak(const char *pat, ...)

       croak_no_modify
               Exactly equivalent to "Perl_croak(aTHX_ "%s", PL_no_modify)",
               but generates terser object code than using "Perl_croak".  Less
               code used on exception code paths reduces CPU cache pressure.

                       void    croak_no_modify()

       croak_sv
               This is an XS interface to Perl's "die" function.

               "baseex" is the error message or object.  If it is a reference,
               it will be used as-is.  Otherwise it is used as a string, and
               if it does not end with a newline then it will be extended with
               some indication of the current location in the code, as
               described for "mess_sv".

               The error message or object will be used as an exception, by
               default returning control to the nearest enclosing "eval", but
               subject to modification by a $SIG{__DIE__} handler.  In any
               case, the "croak_sv" function never returns normally.

               To die with a simple string message, the "croak" function may
               be more convenient.

                       void    croak_sv(SV *baseex)

       die     Behaves the same as "croak", except for the return type.  It
               should be used only where the "OP *" return type is required.
               The function never actually returns.

                       OP *    die(const char *pat, ...)

       die_sv  Behaves the same as "croak_sv", except for the return type.  It
               should be used only where the "OP *" return type is required.
               The function never actually returns.

                       OP *    die_sv(SV *baseex)

       vcroak  This is an XS interface to Perl's "die" function.

               "pat" and "args" are a sprintf-style format pattern and
               encapsulated argument list.  These are used to generate a
               string message.  If the message does not end with a newline,
               then it will be extended with some indication of the current
               location in the code, as described for "mess_sv".

               The error message will be used as an exception, by default
               returning control to the nearest enclosing "eval", but subject
               to modification by a $SIG{__DIE__} handler.  In any case, the
               "croak" function never returns normally.

               For historical reasons, if "pat" is null then the contents of
               "ERRSV" ($@) will be used as an error message or object instead
               of building an error message from arguments.  If you want to
               throw a non-string object, or build an error message in an SV
               yourself, it is preferable to use the "croak_sv" function,
               which does not involve clobbering "ERRSV".

                       void    vcroak(const char *pat, va_list *args)

       vwarn   This is an XS interface to Perl's "warn" function.

               "pat" and "args" are a sprintf-style format pattern and
               encapsulated argument list.  These are used to generate a
               string message.  If the message does not end with a newline,
               then it will be extended with some indication of the current
               location in the code, as described for "mess_sv".

               The error message or object will by default be written to
               standard error, but this is subject to modification by a
               $SIG{__WARN__} handler.

               Unlike with "vcroak", "pat" is not permitted to be null.

                       void    vwarn(const char *pat, va_list *args)

       warn    This is an XS interface to Perl's "warn" function.

               Take a sprintf-style format pattern and argument list.  These
               are used to generate a string message.  If the message does not
               end with a newline, then it will be extended with some
               indication of the current location in the code, as described
               for "mess_sv".

               The error message or object will by default be written to
               standard error, but this is subject to modification by a
               $SIG{__WARN__} handler.

               Unlike with "croak", "pat" is not permitted to be null.

                       void    warn(const char *pat, ...)

       warn_sv This is an XS interface to Perl's "warn" function.

               "baseex" is the error message or object.  If it is a reference,
               it will be used as-is.  Otherwise it is used as a string, and
               if it does not end with a newline then it will be extended with
               some indication of the current location in the code, as
               described for "mess_sv".

               The error message or object will by default be written to
               standard error, but this is subject to modification by a
               $SIG{__WARN__} handler.

               To warn with a simple string message, the "warn" function may
               be more convenient.

                       void    warn_sv(SV *baseex)

Undocumented functions
       The following functions have been flagged as part of the public API,
       but are currently undocumented.  Use them at your own risk, as the
       interfaces are subject to change.  Functions that are not listed in
       this document are not intended for public use, and should NOT be used
       under any circumstances.

       If you feel you need to use one of these functions, first send email to
       perl5-porters@perl.org <mailto:perl5-porters@perl.org>.  It may be that
       there is a good reason for the function not being documented, and it
       should be removed from this list; or it may just be that no one has
       gotten around to documenting it.  In the latter case, you will be asked
       to submit a patch to document the function.  Once your patch is
       accepted, it will indicate that the interface is stable (unless it is
       explicitly marked otherwise) and usable by you.

       GetVars
       Gv_AMupdate
       PerlIO_clearerr
       PerlIO_close
       PerlIO_context_layers
       PerlIO_eof
       PerlIO_error
       PerlIO_fileno
       PerlIO_fill
       PerlIO_flush
       PerlIO_get_base
       PerlIO_get_bufsiz
       PerlIO_get_cnt
       PerlIO_get_ptr
       PerlIO_read
       PerlIO_seek
       PerlIO_set_cnt
       PerlIO_set_ptrcnt
       PerlIO_setlinebuf
       PerlIO_stderr
       PerlIO_stdin
       PerlIO_stdout
       PerlIO_tell
       PerlIO_unread
       PerlIO_write
       _variant_byte_number
       amagic_call
       amagic_deref_call
       any_dup
       atfork_lock
       atfork_unlock
       av_arylen_p
       av_iter_p
       block_gimme
       call_atexit
       call_list
       calloc
       cast_i32
       cast_iv
       cast_ulong
       cast_uv
       ck_warner
       ck_warner_d
       ckwarn
       ckwarn_d
       clear_defarray
       clone_params_del
       clone_params_new
       croak_memory_wrap
       croak_nocontext
       csighandler
       cx_dump
       cx_dup
       cxinc
       deb
       deb_nocontext
       debop
       debprofdump
       debstack
       debstackptrs
       delimcpy
       despatch_signals
       die_nocontext
       dirp_dup
       do_aspawn
       do_binmode
       do_close
       do_gv_dump
       do_gvgv_dump
       do_hv_dump
       do_join
       do_magic_dump
       do_op_dump
       do_open
       do_open9
       do_openn
       do_pmop_dump
       do_spawn
       do_spawn_nowait
       do_sprintf
       do_sv_dump
       doing_taint
       doref
       dounwind
       dowantarray
       dump_eval
       dump_form
       dump_indent
       dump_mstats
       dump_sub
       dump_vindent
       filter_add
       filter_del
       filter_read
       foldEQ_latin1
       form_nocontext
       fp_dup
       fprintf_nocontext
       free_global_struct
       free_tmps
       get_context
       get_mstats
       get_op_descs
       get_op_names
       get_ppaddr
       get_vtbl
       gp_dup
       gp_free
       gp_ref
       gv_AVadd
       gv_HVadd
       gv_IOadd
       gv_SVadd
       gv_add_by_type
       gv_autoload4
       gv_autoload_pv
       gv_autoload_pvn
       gv_autoload_sv
       gv_check
       gv_dump
       gv_efullname
       gv_efullname3
       gv_efullname4
       gv_fetchfile
       gv_fetchfile_flags
       gv_fetchpv
       gv_fetchpvn_flags
       gv_fetchsv
       gv_fullname
       gv_fullname3
       gv_fullname4
       gv_handler
       gv_name_set
       he_dup
       hek_dup
       hv_common
       hv_common_key_len
       hv_delayfree_ent
       hv_eiter_p
       hv_eiter_set
       hv_free_ent
       hv_ksplit
       hv_name_set
       hv_placeholders_get
       hv_placeholders_set
       hv_rand_set
       hv_riter_p
       hv_riter_set
       ibcmp_utf8
       init_global_struct
       init_stacks
       init_tm
       instr
       is_lvalue_sub
       leave_scope
       load_module_nocontext
       magic_dump
       malloc
       markstack_grow
       mess_nocontext
       mfree
       mg_dup
       mg_size
       mini_mktime
       moreswitches
       mro_get_from_name
       mro_get_private_data
       mro_set_mro
       mro_set_private_data
       my_atof
       my_atof2
       my_atof3
       my_chsize
       my_cxt_index
       my_cxt_init
       my_dirfd
       my_exit
       my_failure_exit
       my_fflush_all
       my_fork
       my_lstat
       my_pclose
       my_popen
       my_popen_list
       my_setenv
       my_socketpair
       my_stat
       my_strftime
       newANONATTRSUB
       newANONHASH
       newANONLIST
       newANONSUB
       newATTRSUB
       newAVREF
       newCVREF
       newFORM
       newGVREF
       newGVgen
       newGVgen_flags
       newHVREF
       newHVhv
       newIO
       newMYSUB
       newPROG
       newRV
       newSUB
       newSVREF
       newSVpvf_nocontext
       newSVsv_flags
       new_stackinfo
       op_refcnt_lock
       op_refcnt_unlock
       parser_dup
       perl_alloc_using
       perl_clone_using
       pmop_dump
       pop_scope
       pregcomp
       pregexec
       pregfree
       pregfree2
       printf_nocontext
       ptr_table_fetch
       ptr_table_free
       ptr_table_new
       ptr_table_split
       ptr_table_store
       push_scope
       re_compile
       re_dup_guts
       re_intuit_start
       re_intuit_string
       realloc
       reentrant_free
       reentrant_init
       reentrant_retry
       reentrant_size
       ref
       reg_named_buff_all
       reg_named_buff_exists
       reg_named_buff_fetch
       reg_named_buff_firstkey
       reg_named_buff_nextkey
       reg_named_buff_scalar
       regdump
       regdupe_internal
       regexec_flags
       regfree_internal
       reginitcolors
       regnext
       repeatcpy
       rsignal
       rsignal_state
       runops_debug
       runops_standard
       rvpv_dup
       safesyscalloc
       safesysfree
       safesysmalloc
       safesysrealloc
       save_I16
       save_I32
       save_I8
       save_adelete
       save_aelem
       save_aelem_flags
       save_alloc
       save_aptr
       save_ary
       save_bool
       save_clearsv
       save_delete
       save_destructor
       save_destructor_x
       save_freeop
       save_freepv
       save_freesv
       save_generic_pvref
       save_generic_svref
       save_hash
       save_hdelete
       save_helem
       save_helem_flags
       save_hints
       save_hptr
       save_int
       save_item
       save_iv
       save_list
       save_long
       save_mortalizesv
       save_nogv
       save_op
       save_padsv_and_mortalize
       save_pptr
       save_pushi32ptr
       save_pushptr
       save_pushptrptr
       save_re_context
       save_scalar
       save_set_svflags
       save_shared_pvref
       save_sptr
       save_svref
       save_vptr
       savestack_grow
       savestack_grow_cnt
       scan_num
       scan_vstring
       seed
       set_context
       share_hek
       si_dup
       ss_dup
       stack_grow
       start_subparse
       str_to_version
       sv_2iv
       sv_2pv
       sv_2uv
       sv_catpvf_mg_nocontext
       sv_catpvf_nocontext
       sv_dup
       sv_dup_inc
       sv_peek
       sv_pvn_nomg
       sv_setpvf_mg_nocontext
       sv_setpvf_nocontext
       sys_init
       sys_init3
       sys_intern_clear
       sys_intern_dup
       sys_intern_init
       sys_term
       taint_env
       taint_proper
       unlnk
       unsharepvn
       uvuni_to_utf8
       vdeb
       vform
       vload_module
       vnewSVpvf
       vwarner
       warn_nocontext
       warner
       warner_nocontext
       whichsig
       whichsig_pv
       whichsig_pvn
       whichsig_sv

AUTHORS
       Until May 1997, this document was maintained by Jeff Okamoto
       <okamoto@corp.hp.com>.  It is now maintained as part of Perl itself.

       With lots of help and suggestions from Dean Roehrich, Malcolm Beattie,
       Andreas Koenig, Paul Hudson, Ilya Zakharevich, Paul Marquess, Neil
       Bowers, Matthew Green, Tim Bunce, Spider Boardman, Ulrich Pfeifer,
       Stephen McCamant, and Gurusamy Sarathy.

       API Listing originally by Dean Roehrich <roehrich@cray.com>.

       Updated to be autogenerated from comments in the source by Benjamin
       Stuhl.

SEE ALSO
       perlguts, perlxs, perlxstut, perlintern

perl v5.30.0                      2023-11-23                        PERLAPI(1)
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