perl594delta


DESCRIPTION
       This document describes differences between the 5.9.3 and the 5.9.4
       development releases. See perl590delta, perl591delta, perl592delta and
       perl593delta for the differences between 5.8.0 and 5.9.3.

Incompatible Changes
   chdir FOO
       A bareword argument to chdir() is now recognized as a file handle.
       Earlier releases interpreted the bareword as a directory name.  (Gisle
       Aas)

   Handling of pmc files
       An old feature of perl was that before "require" or "use" look for a
       file with a .pm extension, they will first look for a similar filename
       with a .pmc extension. If this file is found, it will be loaded in
       place of any potentially existing file ending in a .pm extension.

       Previously, .pmc files were loaded only if more recent than the
       matching .pm file. Starting with 5.9.4, they'll be always loaded if
       they exist. (This trick is used by Pugs.)

   @- and @+ in patterns
       The special arrays "@-" and "@+" are no longer interpolated in regular
       expressions. (Sadahiro Tomoyuki)

   $AUTOLOAD can now be tainted
       If you call a subroutine by a tainted name, and if it defers to an
       AUTOLOAD function, then $AUTOLOAD will be (correctly) tainted.  (Rick
       Delaney)

Core Enhancements
   state() variables
       A new class of variables has been introduced. State variables are
       similar to "my" variables, but are declared with the "state" keyword in
       place of "my". They're visible only in their lexical scope, but their
       value is persistent: unlike "my" variables, they're not undefined at
       scope entry, but retain their previous value. (Rafael Garcia-Suarez)

       To use state variables, one needs to enable them by using

           use feature "state";

       or by using the "-E" command-line switch in one-liners.

       See "Persistent variables via state()" in perlsub.

   UNIVERSAL::DOES()
       The "UNIVERSAL" class has a new method, "DOES()". It has been added to
       solve semantic problems with the "isa()" method. "isa()" checks for
       inheritance, while "DOES()" has been designed to be overridden when
       module authors use other types of relations between classes (in
       addition to inheritance). (chromatic)

       working until now. See "require" in perlfunc for details. (Nicholas
       Clark)

   MAD
       MAD, which stands for Misc Attribute Decoration, is a still-in-
       development work leading to a Perl 5 to Perl 6 converter. To enable it,
       it's necessary to pass the argument "-Dmad" to Configure. The obtained
       perl isn't binary compatible with a regular perl 5.9.4, and has space
       and speed penalties; moreover not all regression tests still pass with
       it. (Larry Wall, Nicholas Clark)

Modules and Pragmas
       o   "encoding::warnings" is now a lexical pragma. (Although on older
           perls, which don't have support for lexical pragmas, it keeps its
           global behaviour.) (Audrey Tang)

       o   "threads" is now a dual-life module, also available on CPAN. It has
           been expanded in many ways. A kill() method is available for thread
           signalling.  One can get thread status, or the list of running or
           joinable threads.

           A new "threads->exit()" method is used to exit from the application
           (this is the default for the main thread) or from the current
           thread only (this is the default for all other threads). On the
           other hand, the exit() built-in now always causes the whole
           application to terminate. (Jerry D. Hedden)

   New Core Modules
       o   "Hash::Util::FieldHash", by Anno Siegel, has been added. This
           module provides support for field hashes: hashes that maintain an
           association of a reference with a value, in a thread-safe garbage-
           collected way.  Such hashes are useful to implement inside-out
           objects.

       o   "Module::Build", by Ken Williams, has been added. It's an
           alternative to "ExtUtils::MakeMaker" to build and install perl
           modules.

       o   "Module::Load", by Jos Boumans, has been added. It provides a
           single interface to load Perl modules and .pl files.

       o   "Module::Loaded", by Jos Boumans, has been added. It's used to mark
           modules as loaded or unloaded.

       o   "Package::Constants", by Jos Boumans, has been added. It's a simple
           helper to list all constants declared in a given package.

       o   "Win32API::File", by Tye McQueen, has been added (for Windows
           builds).  This module provides low-level access to Win32 system API
           calls for files/dirs.

Utility Changes
   config_data
       "config_data" is a new utility that comes with "Module::Build". It
       the Perl regular expression engine.

   New manpage, perlunitut
       The perlunitut manpage is an tutorial for programming with Unicode and
       string encodings in Perl, courtesy of Juerd Waalboer.

Performance Enhancements
   Memory optimisations
       Several internal data structures (typeglobs, GVs, CVs, formats) have
       been restructured to use less memory. (Nicholas Clark)

   UTF-8 cache optimisation
       The UTF-8 caching code is now more efficient, and used more often.
       (Nicholas Clark)

   Regular expressions
       Engine de-recursivised
           The regular expression engine is no longer recursive, meaning that
           patterns that used to overflow the stack will either die with
           useful explanations, or run to completion, which, since they were
           able to blow the stack before, will likely take a very long time to
           happen. If you were experiencing the occasional stack overflow (or
           segfault) and upgrade to discover that now perl apparently hangs
           instead, look for a degenerate regex. (Dave Mitchell)

       Single char char-classes treated as literals
           Classes of a single character are now treated the same as if the
           character had been used as a literal, meaning that code that uses
           char-classes as an escaping mechanism will see a speedup. (Yves
           Orton)

       Trie optimisation of literal string alternations
           Alternations, where possible, are optimised into more efficient
           matching structures. String literal alternations are merged into a
           trie and are matched simultaneously.  This means that instead of
           O(N) time for matching N alternations at a given point the new code
           performs in O(1) time. (Yves Orton)

           Note: Much code exists that works around perl's historic poor
           performance on alternations. Often the tricks used to do so will
           disable the new optimisations. Hopefully the utility modules used
           for this purpose will be educated about these new optimisations by
           the time 5.10 is released.

       Aho-Corasick start-point optimisation
           When a pattern starts with a trie-able alternation and there aren't
           better optimisations available the regex engine will use Aho-
           Corasick matching to find the start point. (Yves Orton)

   Sloppy stat on Windows
       On Windows, perl's stat() function normally opens the file to determine
       the link count and update attributes that may have been changed through
       hard links. Setting ${^WIN32_SLOPPY_STAT} to a true value speeds up
       stat() by not performing this operation. (Jan Dubois)
       install is done to the original configured prefix.

   Ports
       Many improvements have been made towards making Perl work correctly on
       z/OS.

       Perl has been reported to work on DragonFlyBSD.

   Compilation improvements
       All ppport.h files in the XS modules bundled with perl are now
       autogenerated at build time. (Marcus Holland-Moritz)

   New probes
       The configuration process now detects whether strlcat() and strlcpy()
       are available.  When they are not available, perl's own version is used
       (from Russ Allbery's public domain implementation).  Various places in
       the perl interpreter now use them. (Steve Peters)

   Windows build improvements
       Building XS extensions
           Support for building XS extension modules with the free MinGW
           compiler has been improved in the case where perl itself was built
           with the Microsoft VC++ compiler. (ActiveState)

       Support for 64-bit compiler
           Support for building perl with Microsoft's 64-bit compiler has been
           improved. (ActiveState)

Selected Bug Fixes
   PERL5SHELL and tainting
       On Windows, the PERL5SHELL environment variable is now checked for
       taintedness. (Rafael Garcia-Suarez)

   Using *FILE{IO}
       "stat()" and "-X" filetests now treat *FILE{IO} filehandles like *FILE
       filehandles. (Steve Peters)

   Overloading and reblessing
       Overloading now works when references are reblessed into another class.
       Internally, this has been implemented by moving the flag for
       "overloading" from the reference to the referent, which logically is
       where it should always have been. (Nicholas Clark)

   Overloading and UTF-8
       A few bugs related to UTF-8 handling with objects that have
       stringification overloaded have been fixed. (Nicholas Clark)

   eval memory leaks fixed
       Traditionally, "eval 'syntax error'" has leaked badly. Many (but not
       all) of these leaks have now been eliminated or reduced. (Dave
       Mitchell)

   Random device on Windows
       In previous versions, perl would read the file /dev/urandom if it
       the perl core, but remain around because modules out there might still
       use them. They come from a factorization effort: for example, many PP
       functions are now shared for several ops.

       The implementation of the special variables $^H and %^H has changed, to
       allow implementing lexical pragmas in pure perl.

Known Problems
       One warning test (number 263 in lib/warnings.t) fails under UTF-8
       locales.

       Bytecode tests fail under several platforms. We are considering
       removing support for byteloader and compiler before the 5.10.0 release.

Reporting Bugs
       If you find what you think is a bug, you might check the articles
       recently posted to the comp.lang.perl.misc newsgroup and the perl bug
       database at http://rt.perl.org/rt3/ .  There may also be information at
       http://www.perl.org/ , the Perl Home Page.

       If you believe you have an unreported bug, please run the perlbug
       program included with your release.  Be sure to trim your bug down to a
       tiny but sufficient test case.  Your bug report, along with the output
       of "perl -V", will be sent off to perlbug@perl.org to be analysed by
       the Perl porting team.

SEE ALSO
       The Changes file for 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                   PERL594DELTA(1)
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