This document describes differences between the 5.10.0 release and the
       5.11.0 development release.

Incompatible Changes
   Unicode interpretation of \w, \d, \s, and the POSIX character classes
       Previous versions of Perl tried to map POSIX style character class
       definitions onto Unicode property names so that patterns would "dwim"
       when matches were made against latin-1 or unicode strings. This proved
       to be a mistake, breaking character class negation, causing forward
       compatibility problems (as Unicode keeps updating their property
       definitions and adding new characters), and other problems.

       Therefore we have now defined a new set of artificial "unicode"
       property names which will be used to do unicode matching of patterns
       using POSIX style character classes and perl short-form escape
       character classes like \w and \d.

       The key change here is that \d will no longer match every digit in the
       unicode standard (there are thousands) nor will \w match every word
       character in the standard, instead they will match precisely their
       POSIX or Perl definition.

       Those needing to match based on Unicode properties can continue to do
       so by using the \p{} syntax to match whichever property they like,
       including the new artificial definitions.

       NOTE: This is a backwards incompatible no-warning change in behaviour.
       If you are upgrading and you process large volumes of text look for
       POSIX and Perl style character classes and change them to the relevant
       property name (by removing the word 'Posix' from the current name).

       The following table maps the POSIX character class names, the escapes
       and the old and new Unicode property mappings:

           POSIX  Esc  Class               New-Property  ! Old-Property
           alnum       [0-9A-Za-z]         IsPosixAlnum  ! IsAlnum
           alpha       [A-Za-z]            IsPosixAlpha  ! IsAlpha
           ascii       [\000-\177]         IsASCII       = IsASCII
           blank       [\011 ]             IsPosixBlank  !
           cntrl       [\0-\37\177]        IsPosixCntrl  ! IsCntrl
           digit   \d  [0-9]               IsPosixDigit  ! IsDigit
           graph       [!-~]               IsPosixGraph  ! IsGraph
           lower       [a-z]               IsPosixLower  ! IsLower
           print       [ -~]               IsPosixPrint  ! IsPrint
           punct       [!-/:-@[-`{-~]      IsPosixPunct  ! IsPunct
           space       [\11-\15 ]          IsPosixSpace  ! IsSpace
                   \s  [\11\12\14\15 ]     IsPerlSpace   ! IsSpacePerl
           upper       [A-Z]               IsPosixUpper  ! IsUpper
           word    \w  [0-9A-Z_a-z]        IsPerlWord    ! IsWord
           xdigit      [0-9A-Fa-f]         IsXDigit      = IsXDigit

       In @INC, ARCHLIB and PRIVLIB now occur after after the current
       version's site_perl and vendor_perl.

   Switch statement changes
       The handling of complex expressions by the "given"/"when" switch
       statement has been enhanced. These enhancements are also available in
       5.10.1 and subsequent 5.10 releases. There are two new cases where
       "when" now interprets its argument as a boolean, instead of an
       expression to be used in a smart match:

       flip-flop operators
           The ".." and "..." flip-flop operators are now evaluated in boolean
           context, following their usual semantics; see "Range Operators" in

           Note that, as in perl 5.10.0, "when (1..10)" will not work to test
           whether a given value is an integer between 1 and 10; you should
           use "when ([1..10])" instead (note the array reference).

           However, contrary to 5.10.0, evaluating the flip-flop operators in
           boolean context ensures it can now be useful in a "when()", notably
           for implementing bistable conditions, like in:

               when (/^=begin/ .. /^=end/) {
                 # do something

       defined-or operator
           A compound expression involving the defined-or operator, as in
           "when (expr1 // expr2)", will be treated as boolean if the first
           expression is boolean. (This just extends the existing rule that
           applies to the regular or operator, as in "when (expr1 || expr2)".)

       The next section details more changes brought to the semantics to the
       smart match operator, that naturally also modify the behaviour of the
       switch statements where smart matching is implicitly used.  These
       changers were also made for the 5.10.1 release, and will remain in
       subsequent 5.10 releases.

   Smart match changes
       Changes to type-based dispatch

       The smart match operator "~~" is no longer commutative. The behaviour
       of a smart match now depends primarily on the type of its right hand
       argument. Moreover, its semantics have been adjusted for greater
       consistency or usefulness in several cases. While the general backwards
       compatibility is maintained, several changes must be noted:

       o   Code references with an empty prototype are no longer treated
           specially.  They are passed an argument like the other code
           references (even if they choose to ignore it).

       o   "%hash ~~ sub {}" and "@array ~~ sub {}" now test that the
           subroutine returns a true value for each key of the hash (or
           the elements of the array. It's true if one element in @array
           verifies "$scalar ~~ $element". This is a generalization of the old
           behaviour that tested whether the array contained the scalar.

       The full dispatch table for the smart match operator is given in "Smart
       matching in detail" in perlsyn.

       Smart match and overloading

       According to the rule of dispatch based on the rightmost argument type,
       when an object overloading "~~" appears on the right side of the
       operator, the overload routine will always be called (with a 3rd
       argument set to a true value, see overload.) However, when the object
       will appear on the left, the overload routine will be called only when
       the rightmost argument is a simple scalar. This way distributivity of
       smart match across arrays is not broken, as well as the other
       behaviours with complex types (coderefs, hashes, regexes). Thus,
       writers of overloading routines for smart match mostly need to worry
       only with comparing against a scalar, and possibly with stringification
       overloading; the other common cases will be automatically handled

       "~~" will now refuse to work on objects that do not overload it (in
       order to avoid relying on the object's underlying structure). (However,
       if the object overloads the stringification or the numification
       operators, and if overload fallback is active, it will be used instead,
       as usual.)

   Labels can't be keywords
       Labels used as targets for the "goto", "last", "next" or "redo"
       statements cannot be keywords anymore. This restriction will prevent
       potential confusion between the "goto LABEL" and "goto EXPR" syntaxes:
       for example, a statement like "goto print" would jump to a label whose
       name would be the return value of "print()", (usually 1), instead of a
       label named "print". Moreover, the other control flow statements would
       just ignore any keyword passed to them as a label name. Since such
       labels cannot be defined anymore, this kind of error will be avoided.

   Other incompatible changes
       o   The semantics of "use feature :5.10*" have changed slightly.  See
           "Modules and Pragmata" for more information.

       o   It is now a run-time error to use the smart match operator "~~"
           with an object that has no overload defined for it. (This way "~~"
           will not break encapsulation by matching against the object's
           internal representation as a reference.)

       o   The version control system used for the development of the perl
           interpreter has been switched from Perforce to git.  This is mainly
           an internal issue that only affects people actively working on the
           perl core; but it may have minor external visibility, for example
           in some of details of the output of "perl -V". See perlrepository
           for more information.

           "Test::Harness::Straps" module has been removed.  See "Updated
           Modules" for more details.

       o   As part of the "ExtUtils::MakeMaker" upgrade, the
           "ExtUtils::MakeMaker::bytes" and "ExtUtils::MakeMaker::vmsish"
           modules have been removed from this distribution.

       o   "Module::CoreList" no longer contains the %:patchlevel hash.

       o   This one is actually a change introduced in 5.10.0, but it was
           missed from that release's perldelta, so it is mentioned here

           A bugfix related to the handling of the "/m" modifier and "qr"
           resulted in a change of behaviour between 5.8.x and 5.10.0:

               # matches in 5.8.x, doesn't match in 5.10.0
               $re = qr/^bar/; "foo\nbar" =~ /$re/m;

       o   "length undef" now returns undef.

       o   Unsupported private C API functions are now declared "static" to
           prevent leakage to Perl's public API.

       o   To support the bootstrapping process, miniperl no longer builds
           with UTF-8 support in the regexp engine.

           This allows a build to complete with PERL_UNICODE set and a UTF-8
           locale.  Without this there's a bootstrapping problem, as miniperl
           can't load the UTF-8 components of the regexp engine, because
           they're not yet built.

       o   miniperl's @INC is now restricted to just -I..., the split of
           $ENV{PERL5LIB}, and "."

       o   A space or a newline is now required after a "#line XXX" directive.

       o   Tied filehandles now have an additional method EOF which provides
           the EOF type

       o   To better match all other flow control statements, "foreach" may no
           longer be used as an attribute.

Core Enhancements
   Unicode Character Database 5.1.0
       The copy of the Unicode Character Database included in Perl 5.11.0 has
       been updated to 5.1.0 from 5.0.0. See
       <> for the
       notable changes.

   A proper interface for pluggable Method Resolution Orders
       As of Perl 5.11.0 there is a new interface for plugging and using
       method resolution orders other than the default (linear depth first
       search).  The C3 method resolution order added in 5.10.0 has been re-
       name is coming, so compatibility is preserved.) (Rafael Garcia-Suarez)

   Implicit strictures
       Using the "use VERSION" syntax with a version number greater or equal
       to 5.11.0 will also lexically enable strictures just like "use strict"
       would do (in addition to enabling features.) So, the following:

           use 5.11.0;

       will now imply:

           use strict;
           use feature ':5.11';

   Parallel tests
       The core distribution can now run its regression tests in parallel on
       Unix-like platforms. Instead of running "make test", set "TEST_JOBS" in
       your environment to the number of tests to run in parallel, and run
       "make test_harness". On a Bourne-like shell, this can be done as

           TEST_JOBS=3 make test_harness  # Run 3 tests in parallel

       An environment variable is used, rather than parallel make itself,
       because TAP::Harness needs to be able to schedule individual non-
       conflicting test scripts itself, and there is no standard interface to
       "make" utilities to interact with their job schedulers.

       Note that currently some test scripts may fail when run in parallel
       (most notably "ext/IO/t/io_dir.t"). If necessary run just the failing
       scripts again sequentially and see if the failures go away.

   The "..." operator
       A new operator, "...", nicknamed the Yada Yada operator, has been
       added.  It is intended to mark placeholder code, that is not yet
       implemented.  See "Yada Yada Operator" in perlop. (chromatic)

   DTrace support
       Some support for DTrace has been added. See "DTrace support" in

   Support for "configure_requires" in CPAN module metadata
       Both "CPAN" and "CPANPLUS" now support the "configure_requires" keyword
       in the META.yml metadata file included in most recent CPAN
       distributions.  This allows distribution authors to specify
       configuration prerequisites that must be installed before running
       Makefile.PL or Build.PL.

       See the documentation for "ExtUtils::MakeMaker" or "Module::Build" for
       more on how to specify "configure_requires" when creating a
       distribution for CPAN.

   "each" is now more flexible
       The "each" function can now operate on arrays.

   "delete local"
       "delete local" now allows you to locally delete a hash entry.

   New support for Abstract namespace sockets
       Abstract namespace sockets are Linux-specific socket type that live in
       AF_UNIX family, slightly abusing it to be able to use arbitrary
       character arrays as addresses: They start with nul byte and are not
       terminated by nul byte, but with the length passed to the socket()
       system call.

Modules and Pragmata
   Dual-lifed modules moved
       Dual-lifed modules maintained primarily in the Perl core now live in
       dist/.  Dual-lifed modules maintained primarily on CPAN now live in

       In previous releases of Perl, it was customary to enumerate all module
       changes in this section of the "perldelta" file.   From 5.11.0 forward
       only notable updates (such as new or deprecated modules ) will be
       listed in this section. For a complete reference to the versions of
       modules shipped in a given release of perl, please see

   New Modules and Pragmata
           This is a new lexically-scoped alternative for the "Fatal" module.
           The bundled version is 2.06_01. Note that in this release, using a
           string eval when "autodie" is in effect can cause the autodie
           behaviour to leak into the surrounding scope. See "BUGS" in autodie
           for more details.

           This has been added to the core (version 2.020).

           This pragma establishes an ISA relationship with base classes at
           compile time. It provides the key feature of "base" without the
           feature creep.

           This has been added to the core (version 1.39).

   Pragmata Changes
           See "The "overloading" pragma" above.

           The "attrs" pragma has been removed. It had been marked as
           deprecated since 5.6.0.

           The Unicode NameAliases.txt database file has been added. This has
           the effect of adding some extra "\N" character names that formerly
           Upgraded from version 1.00 to 1.01. Performance for single
           inheritance is 40% faster - see "Performance Enhancements" below.

           "mro" is now implemented as an XS extension. The documented
           interface has not changed. Code relying on the implementation
           detail that some "mro::" methods happened to be available at all
           times gets to "keep both pieces".

   Updated Modules
           Upgraded from version 6.42 to 6.55_02.

           Note that "ExtUtils::MakeMaker::bytes" and
           "ExtUtils::MakeMaker::vmsish" have been removed from this

           Upgraded from version 2.64 to 3.17.

           Note that one side-effect of the 2.x to 3.x upgrade is that the
           experimental "Test::Harness::Straps" module (and its supporting
           "Assert", "Iterator", "Point" and "Results" modules) have been
           removed. If you still need this, then they are available in the
           (unmaintained) "Test-Harness-Straps" distribution on CPAN.

           Upgraded from version 1.04 to 1.05.

           "UNIVERSAL->import()" is now deprecated.

Utility Changes
           Now looks in "include-fixed" too, which is a recent addition to
           gcc's search path.

           No longer incorrectly treats enum values like macros (Daniel Burr).

           Now handles C++ style constants ("//") properly in enums. (A patch
           from Rainer Weikusat was used; Daniel Burr also proposed a similar
           "LVALUE" subroutines now work under the debugger.

           The debugger now correctly handles proxy constant subroutines, and
           subroutine stubs.

           perlbug now uses %Module::CoreList::bug_tracker to print out
           upstream bug tracker URLs.

           Where the user names a module that their bug report is about, and
           we know the URL for its upstream bug tracker, provide a message to

           This describes the new interface for pluggable Method Resolution

           This document, by Richard Foley, provides an introduction to the
           use of performance and optimization techniques which can be used
           with particular reference to perl programs.

           This describes how to access the perl source using the git version
           control system.

Changes to Existing Documentation
       The various large Changes* files (which listed every change made to
       perl over the last 18 years) have been removed, and replaced by a small
       file, also called Changes, which just explains how that same
       information may be extracted from the git version control system.

       The file Porting/patching.pod has been deleted, as it mainly described
       interacting with the old Perforce-based repository, which is now
       obsolete.  Information still relevant has been moved to perlrepository.

       perlapi, perlintern, perlmodlib and perltoc are now all generated at
       build time, rather than being shipped as part of the release.

       o   Documented -X overloading.

       o   Documented that "when()" treats specially most of the filetest

       o   Documented when as a syntax modifier

       o   Eliminated "Old Perl threads tutorial", which describes 5005

           pod/perlthrtut.pod is the same material reworked for ithreads.

       o   Correct previous documentation: v-strings are not deprecated

           With version objects, we need them to use MODULE VERSION syntax.
           This patch removes the deprecation note.

       o   Added security contact information to perlsec

Performance Enhancements
       o   A new internal cache means that "isa()" will often be faster.

       o   The implementation of "C3" Method Resolution Order has been
           optimised - linearisation for classes with single inheritance is
           40% faster. Performance for multiple inheritance is unchanged.

   ext/ reorganisation
       The layout of directories in ext has been revised. Specifically, all
       extensions are now flat, and at the top level, with "/" in pathnames
       replaced by "-", so that ext/Data/Dumper/ is now ext/Data-Dumper/, etc.
       The names of the extensions as specified to Configure, and as reported
       by %Config::Config under the keys "dynamic_ext", "known_extensions",
       "nonxs_ext" and "static_ext" have not changed, and still use "/". Hence
       this change will not have any affect once perl is installed. "Safe" has
       been split out from being part of "Opcode", and "mro" is now an
       extension in its own right.

       Nearly all dual-life modules have been moved from lib to ext, and will
       now appear as known "nonxs_ext". This will made no difference to the
       structure of an installed perl, nor will the modules installed differ,
       unless you run Configure with options to specify an exact list of
       extensions to build. In this case, you will rapidly become aware that
       you need to add to your list, because various modules needed to
       complete the build, such as "ExtUtils::ParseXS", have now become
       extensions, and without them the build will fail well before it
       attempts to run the regression tests.

   Configuration improvements
       If "vendorlib" and "vendorarch" are the same, then they are only added
       to @INC once.

       $Config{usedevel} and the C-level "PERL_USE_DEVEL" are now defined if
       perl is built with  "-Dusedevel".

       Configure will enable use of "-fstack-protector", to provide protection
       against stack-smashing attacks, if the compiler supports it.

       Configure will now determine the correct prototypes for re-entrant
       functions, and for "gconvert", if you are using a C++ compiler rather
       than a C compiler.

       On Unix, if you build from a tree containing a git repository, the
       configuration process will note the commit hash you have checked out,
       for display in the output of "perl -v" and "perl -V". Unpushed local
       commits are automatically added to the list of local patches displayed
       by "perl -V".

   Compilation improvements
       As part of the flattening of ext, all extensions on all platforms are
       built by This replaces the Unix-specific
       ext/util/make_ext, VMS-specific and Win32-specific

   Platform Specific Changes
       AIX Removed libbsd for AIX 5L and 6.1. Only "flock()" was used from

           Removed libgdbm for AIX 5L and 6.1. The libgdbm is delivered as an
           optional package with the AIX Toolbox. Unfortunately the 64 bit
           version is broken.
           The hints files now identify the correct threading libraries on
           FreeBSD 7 and later.

           We now work around a bizarre preprocessor bug in the Irix 6.5
           compiler: "cc -E -" unfortunately goes into K&R mode, but "cc -E
           file.c" doesn't.

           Patches from the Haiku maintainers have been merged in. Perl should
           now build on Haiku.

           Support for Tenon Intersystems MachTen Unix layer for MacOS Classic
           was removed in Perl 5.11.0

           Support for Atari MiNT was removed in Perl 5.11.0.

       MirOS BSD
           Perl should now build on MirOS BSD.

           Hints now supports versions 5.*.

       Stratus VOS
           Various changes from Stratus have been merged in.

           There is now support for Symbian S60 3.2 SDK and S60 5.0 SDK.

           Improved message window handling means that "alarm" and "kill"
           messages will no longer be dropped under race conditions.

       VMS Reads from the in-memory temporary files of "PerlIO::scalar" used
           to fail if $/ was set to a numeric reference (to indicate record-
           style reads).  This is now fixed.

           VMS now supports "getgrgid".

           Many improvements and cleanups have been made to the VMS file name
           handling and conversion code.

           Enabling the "PERL_VMS_POSIX_EXIT" logical name now encodes a POSIX
           exit status in a VMS condition value for better interaction with
           GNV's bash shell and other utilities that depend on POSIX exit
           values.  See "$?" in perlvms for details.

           "File::Copy" now detects Unix compatibility mode on VMS.

Selected Bug Fixes
       o   "-I" on shebang line now adds directories in front of @INC as
           documented, and as does "-I" when specified on the command-line.

       o   Fixed memory leak on "while (1) { map 1, 1 }" [RT #53038].

       o   Some potential coredumps in PerlIO fixed [RT #57322,54828].

       o   The debugger now works with lvalue subroutines.

       o   The debugger's "m" command was broken on modules that defined
           constants [RT #61222].

       o   "crypt" and string complement could return tainted values for
           untainted arguments [RT #59998].

       o   The "-i".suffix command-line switch now recreates the file using
           restricted permissions, before changing its mode to match the
           original file. This eliminates a potential race condition [RT

       o   On some Unix systems, the value in $? would not have the top bit
           set ("$? & 128") even if the child core dumped.

       o   Under some circumstances, $^R could incorrectly become undefined
           [RT #57042].

       o   In the XS API, various hash functions, when passed a pre-computed
           hash where the key is UTF-8, might result in an incorrect lookup.

       o   XS code including XSUB.h before perl.h gave a compile-time error
           [RT #57176].

       o   "$object->isa('Foo')" would report false if the package "Foo"
           didn't exist, even if the object's @ISA contained "Foo".

       o   Various bugs in the new-to 5.10.0 mro code, triggered by
           manipulating @ISA, have been found and fixed.

       o   Bitwise operations on references could crash the interpreter, e.g.
           "$x=\$y; $x |= "foo"" [RT #54956].

       o   Patterns including alternation might be sensitive to the internal
           UTF-8 representation, e.g.

               my $byte = chr(192);
               my $utf8 = chr(192); utf8::upgrade($utf8);
               $utf8 =~ /$byte|X}/i;       # failed in 5.10.0

       o   Within UTF8-encoded Perl source files (i.e. where "use utf8" is in
           effect), double-quoted literal strings could be corrupted where a
           "\xNN", "\0NNN" or "\N{}" is followed by a literal character with
           ordinal value greater than 255 [RT #59908].

       o   "B::Deparse" failed to correctly deparse various constructs:
           "readpipe STRING" [RT #62428], "CORE::require(STRING)" [RT #62488],
           "sub foo(_)" [RT #62484].

               ("ab" x 32768) =~ /^(ab)*$/

       o   "shmget" was limited to a 32 bit segment size on a 64 bit OS [RT

       o   Using "next" or "last" to exit a "given" block no longer produces a
           spurious warning like the following:

               Exiting given via last at line 123

       o   On Windows, '.\foo' and '..\foo'  were treated differently than
           './foo' and '../foo' by "do" and "require" [RT #63492].

       o   Assigning a format to a glob could corrupt the format; e.g.:

                *bar=*foo{FORMAT}; # foo format now bad

       o   Attempting to coerce a typeglob to a string or number could cause
           an assertion failure. The correct error message is now generated,
           "Can't coerce GLOB to $type".

       o   Under "use filetest 'access'", "-x" was using the wrong access
           mode. This has been fixed [RT #49003].

       o   "length" on a tied scalar that returned a Unicode value would not
           be correct the first time. This has been fixed.

       o   Using an array "tie" inside in array "tie" could SEGV. This has
           been fixed. [RT #51636]

       o   A race condition inside "PerlIOStdio_close()" has been identified
           and fixed. This used to cause various threading issues, including

       o   In "unpack", the use of "()" groups in scalar context was
           internally placing a list on the interpreter's stack, which
           manifested in various ways, including SEGVs.  This is now fixed [RT

       o   Magic was called twice in "substr", "\&$x", "tie $x, $m" and
           "chop".  These have all been fixed.

       o   A 5.10.0 optimisation to clear the temporary stack within the
           implicit loop of "s///ge" has been reverted, as it turned out to be
           the cause of obscure bugs in seemingly unrelated parts of the
           interpreter [commit ef0d4e17921ee3de].

       o   The line numbers for warnings inside "elsif" are now correct.

       o   The ".." operator now works correctly with ranges whose ends are at
           or close to the values of the smallest and largest integers.

       o   "binmode STDIN, ':raw'" could lead to segmentation faults on some
       o   Using (?|) in a regex could cause a segfault [RT #59734].

       o   Use of a UTF-8 "tr//" within a closure could cause a segfault [RT

       o   Calling "Perl_sv_chop()" or otherwise upgrading an SV could result
           in an unaligned 64-bit access on the SPARC architecture [RT

       o   In the 5.10.0 release, "inc_version_list" would incorrectly list
           "5.10.*" after "5.8.*"; this affected the @INC search order [RT

       o   In 5.10.0, "pack "a*", $tainted_value" returned a non-tainted value
           [RT #52552].

       o   In 5.10.0, "printf" and "sprintf" could produce the fatal error
           "panic: utf8_mg_pos_cache_update" when printing UTF-8 strings [RT

       o   In the 5.10.0 release, a dynamically created "AUTOLOAD" method
           might be missed (method cache issue) [RT #60220,60232].

       o   In the 5.10.0 release, a combination of "use feature" and "//ee"
           could cause a memory leak [RT #63110].

       o   "-C" on the shebang ("#!") line is once more permitted if it is
           also specified on the command line. "-C" on the shebang line used
           to be a silent no-op if it was not also on the command line, so
           perl 5.10.0 disallowed it, which broke some scripts. Now perl
           checks whether it is also on the command line and only dies if it
           is not [RT #67880].

       o   In 5.10.0, certain types of re-entrant regular expression could
           crash, or cause the following assertion failure [RT #60508]:

               Assertion rx->sublen >= (s - rx->subbeg) + i failed

       o   Previously missing files from Unicode 5.1 Character Database are
           now included.

       o   "TMPDIR" is now honored when opening an anonymous temporary file

New or Changed Diagnostics
       "panic: sv_chop %s"
           This new fatal error occurs when the C routine "Perl_sv_chop()" was
           passed a position that is not within the scalar's string buffer.
           This could be caused by buggy XS code, and at this point recovery
           is not possible.

       "Can't locate package %s for the parents of %s"
           This warning has been removed. In general, it only got produced in
           conjunction with other warnings, and removing it allowed an ISA
           lookup optimisation to be added.

       o   TODO: REGEXPs are first class

       o   TODO: OOK is reworked, such that an OOKed scalar is PV not PVIV

       o   The J.R.R. Tolkien quotes at the head of C source file have been
           checked and proper citations added, thanks to a patch from Tom

       o   "Perl_vcroak()" now accepts a null first argument. In addition, a
           full audit was made of the "not NULL" compiler annotations, and
           those for several other internal functions were corrected.

       o   New macros "dSAVEDERRNO", "dSAVE_ERRNO", "SAVE_ERRNO",
           "RESTORE_ERRNO" have been added to formalise the temporary saving
           of the "errno" variable.

       o   The function "Perl_sv_insert_flags" has been added to augment

       o   The function "Perl_newSV_type(type)" has been added, equivalent to
           "Perl_newSV()" followed by "Perl_sv_upgrade(type)".

       o   The function "Perl_newSVpvn_flags()" has been added, equivalent to
           "Perl_newSVpvn()" and then performing the action relevant to the

           Two flag bits are currently supported.

               This will call "SvUTF8_on()" for you. (Note that this does not
               convert an sequence of ISO 8859-1 characters to UTF-8). A
               wrapper, "newSVpvn_utf8()" is available for this.

               Call "Perl_sv_2mortal()" on the new SV.

           There is also a wrapper that takes constant strings,

       o   The function "Perl_croak_xs_usage" has been added as a wrapper to

       o   The functions "PerlIO_find_layer" and "PerlIO_list_alloc" are now

       o   "PL_na" has been exterminated from the core code, replaced by local
           STRLEN temporaries, or "*_nolen()" calls. Either approach is faster
           than "PL_na", which is a pointer deference into the interpreter
           structure under ithreads, and a global variable otherwise.

       o   "Perl_mg_free()" used to leave freed memory accessible via
           "SvMAGIC()" on the scalar. It now updates the linked list to remove
           each piece of magic as it is freed.

       o   SV allocation tracing has been added to the diagnostics enabled by
           "-Dm".  The tracing can alternatively output via the "PERL_MEM_LOG"
           mechanism, if that was enabled when the perl binary was compiled.

       o   Smartmatch resolution tracing has been added as a new diagnostic.
           Use "-DM" to enable it.

       o   A new debugging flag "-DB" now dumps subroutine definitions,
           leaving "-Dx" for its original purpose of dumping syntax trees.

       o   Uses of "Nullav", "Nullcv", "Nullhv", "Nullop", "Nullsv" etc have
           been replaced by "NULL" in the core code, and non-dual-life
           modules, as "NULL" is clearer to those unfamiliar with the core

       o   A macro MUTABLE_PTR(p) has been added, which on (non-pedantic) gcc
           will not cast away "const", returning a "void *". Macros
           "MUTABLE_SV(av)", "MUTABLE_SV(cv)" etc build on this, casting to
           "AV *" etc without casting away "const". This allows proper
           compile-time auditing of "const" correctness in the core, and
           helped picked up some errors (now fixed).

       o   Macros "mPUSHs()" and "mXPUSHs()" have been added, for pushing SVs
           on the stack and mortalizing them.

       o   Use of the private structure "mro_meta" has changed slightly.
           Nothing outside the core should be accessing this directly anyway.

       o   A new tool, Porting/ has been added, that allows you
           to view how a C preprocessor macro would be expanded when compiled.
           This is handy when trying to decode the macro hell that is the perl

New Tests
       Many modules updated from CPAN incorporate new tests.

       Several tests that have the potential to hang forever if they fail now
       incorporate a "watchdog" functionality that will kill them after a
       timeout, which helps ensure that "make test" and "make test_harness"
       run to completion automatically. (Jerry Hedden).

       Some core-specific tests have been added:

           Check that the debugger can retain source lines from "eval".

           Check that bad layers fail.

           Check that PerlIO layers are not leaking.

           Tests for "dbmopen" and "dbmclose".

           Tests for the interaction of "index" and threads.

           Tests for the interaction of esoteric patterns and threads.

           Test that "qr" doesn't leak.

           Tests for the interaction of regex recursion and threads.

           Tests for the interaction of patterns with embedded "qr//" and

           Tests for Unicode properties in regular expressions.

           Tests for the interaction of Unicode properties and threads.

           Test the tied methods of "Tie::Hash::NamedCapture".

           Check that POSIX character classes behave consistently.

           Check that exportable "re" functions in universal.c work.

           Check that "setpgrp" works.

           Tests for the interaction of "substr" and threads.

           Check that upgrading and assigning scalars works.

           Check that Unicode in the lexer works.

           Check that Unicode and "tie" work.

Known Problems
       This is a list of some significant unfixed bugs, which are regressions
       from either 5.10.0 or 5.8.x.

       o   "List::Util::first" misbehaves in the presence of a lexical $_
               use charnames ':full';
               my $r1 = qr/\N{THAI CHARACTER SARA I}/;
               "foo" =~ $r1;    # okay
               "foo" =~ /$r1+/; # runtime error

           A workaround is to generate the character outside of the regex:

               my $a = "\N{THAI CHARACTER SARA I}";
               my $r1 = qr/$a/;

       o   Some regexes may run much more slowly when run in a child thread
           compared with the thread the pattern was compiled into [RT #55600].

       The following items are now deprecated.

       o   "Switch" is buggy and should be avoided. From perl 5.11.0 onwards,
           it is intended that any use of the core version of this module will
           emit a warning, and that the module will eventually be removed from
           the core (probably in perl 5.14.0). See "Switch statements" in
           perlsyn for its replacement.

       o   The following modules will be removed from the core distribution in
           a future release, and should be installed from CPAN instead.
           Distributions on CPAN which require these should add them to their
           prerequisites. The core versions of these modules warnings will
           issue a deprecation warning.

           o   "Class::ISA"

           o   "Pod::Plainer"

           o   "Shell"

           Currently support to install from CPAN without a force is "TODO" in
           CPAN and CPANPLUS. This will be addressed before 5.12.0 ships.

       o   "suidperl" has been removed. It used to provide a mechanism to
           emulate setuid permission bits on systems that don't support it

       o   Deprecate assignment to $[

       o   Remove attrs, which has been deprecated since 1999/10/02.

       o   Deprecate use of the attribute :locked on subroutines.

       o   Deprecate using "locked" with the attributes pragma.

       o   Deprecate using "unique" with the attributes pragma.

       o   warn if ++ or -- are unable to change the value because it's beyond
           the limit of representation

       o   Unintended interpolation of $\ in regex

       o   Make overflow warnings in gmtime/localtime only occur when warnings
           are on

       o   Improve mro merging error messages.

           They are now very similar to those produced by Algorithm::C3.

       o   Amelioration of the error message "Unrecognized character %s in
           column %d"

           Changes the error message to "Unrecognized character %s; marked by
           <-- HERE after %s<-- HERE near column %d". This should make it a
           little simpler to spot and correct the suspicious character.

       o   Explicitly point to $. when it causes an uninitialized warning for
           ranges in scalar context

       o   Deprecated numerous Perl 4-era libraries:

 ,, and are all now deprecated. Using
           them will incur a warning.

       Some of the work in this release was funded by a TPF grant funded by
       Dijkmat BV, The Netherlands.

       Steffen Mueller and David Golden in particular helped getting CPAN
       modules polished and synchronised with their in-core equivalents.

       Craig Berry was tireless in getting maint to run under VMS, no matter
       how many times we broke it for him.

       The other core committers contributed most of the changes, and applied
       most of the patches sent in by the hundreds of contributors listed in

       Much of the work of categorizing changes in this perldelta file was
       contributed by the following porters using

       Nicholas Clark, leon, shawn, alexm, rjbs, rafl, Pedro Melo, brunorc,
       anonymous, X, Tom Hukins, anonymous, Jesse, dagolden, Moritz Onken,
       Mark Fowler, chorny, anonymous, tmtm

       Finally, thanks to Larry Wall, without whom none of this would be

       If the bug you are reporting has security implications, which make it
       inappropriate to send to a publicly archived mailing list, then please
       send it to This points to a closed
       subscription unarchived mailing list, which includes all the core
       committers, who be able to help assess the impact of issues, figure out
       a resolution, and help co-ordinate the release of patches to mitigate
       or fix the problem across all platforms on which Perl is supported.
       Please only use this address for security issues in the Perl core, not
       for modules independently distributed on CPAN.

       The Changes file for an explanation of how to view exhaustive details
       on what changed.

       The INSTALL file for how to build Perl.

       The README file for general stuff.

       The Artistic and Copying files for copyright information.

perl v5.14.2                      2011-09-26                  PERL5110DELTA(1)
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