=head1 NAME
-perldelta - what is new for perl v5.9.4
+perl594delta - what is new for perl v5.9.4
=head1 DESCRIPTION
This document describes differences between the 5.9.3 and the 5.9.4
-develop
ement releases. See L<perl590delta>, L<perl591delta>, L<perl592delta>
+development releases. See L<perl590delta>, L<perl591delta>, L<perl592delta>
and L<perl593delta> for the differences between 5.8.0 and 5.9.3.
=head1 Incompatible Changes
=head2 chdir FOO
-A bareword argument to chdir is now recognized as a file handle.
+A bareword argument to chdir() is now recognized as a file handle.
Earlier releases interpreted the bareword as a directory name.
+(Gisle Aas)
=head2 Handling of pmc files
-TODO XXX explain what are pmc files
+An old feature of perl was that before C<require> or C<use> look for a
+file with a F<.pm> extension, they will first look for a similar filename
+with a F<.pmc> extension. If this file is found, it will be loaded in
+place of any potentially existing file ending in a F<.pm> extension.
-.pmc files are always loaded, even if they are older than a matching .pm
-file. (This trick is used by Pugs.)
+Previously, F<.pmc> files were loaded only if more recent than the
+matching F<.pm> file. Starting with 5.9.4, they'll be always loaded if
+they exist. (This trick is used by Pugs.)
=head2 @- and @+ in patterns
The special arrays C<@-> and C<@+> are no longer interpolated in regular
-expressions.
+expressions. (Sadahiro Tomoyuki)
=head2 $AUTOLOAD can now be tainted
If you call a subroutine by a tainted name, and if it defers to an
AUTOLOAD function, then $AUTOLOAD will be (correctly) tainted.
+(Rick Delaney)
=head1 Core Enhancements
=head2 state() variables
-=head2 UNIVERSAL:DOES()
+A new class of variables has been introduced. State variables are similar
+to C<my> variables, but are declared with the C<state> keyword in place of
+C<my>. They're visible only in their lexical scope, but their value is
+persistent: unlike C<my> variables, they're not undefined at scope entry,
+but retain their previous value. (Rafael Garcia-Suarez)
-=head1 Modules and Pragmata
+To use state variables, one needs to enable them by using
-C<encoding::warnings> is now a lexical pragma.
+ use feature "state";
-C<threads>
+or by using the C<-E> command-line switch in one-liners.
+
+See L<perlsub/"Persistent variables via state()">.
+
+=head2 UNIVERSAL::DOES()
+
+The C<UNIVERSAL> class has a new method, C<DOES()>. It has been added to
+solve semantic problems with the C<isa()> method. C<isa()> checks for
+inheritance, while C<DOES()> has been designed to be overridden when
+module authors use other types of relations between classes (in addition
+to inheritance). (chromatic)
+
+See L<< UNIVERSAL/"$obj->DOES( ROLE )" >>.
+
+=head2 Exceptions in constant folding
+
+The constant folding routine is now wrapped in an exception handler, and
+if folding throws an exception (such as attempting to evaluate 0/0), perl
+now retains the current optree, rather than aborting the whole program.
+(Nicholas Clark, Dave Mitchell)
+
+=head2 Source filters in @INC
+
+It's possible to enhance the mechanism of subroutine hooks in @INC by
+adding a source filter on top of the filehandle opened and returned by the
+hook. This feature was planned a long time ago, but wasn't quite working
+until now. See L<perlfunc/require> for details. (Nicholas Clark)
+
+=head2 MAD
+
+MAD, which stands for I<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 C<-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)
+
+=head1 Modules and Pragmas
+
+=over 4
+
+=item *
+
+C<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)
+
+=item *
+
+C<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 C<< 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)
+
+=back
=head2 New Core Modules
=item *
-C<Module::Build> has been added.
+C<Hash::Util::FieldHash>, by Anno Siegel, has been added. This module
+provides support for I<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.
=item *
-C<Hash::Util::FieldHash> has been added. This module provides support for
-I<field hashes>: hashes that maintain an association of a reference with a
-value, in a thread-safe garbage-collected way.
+C<Module::Build>, by Ken Williams, has been added. It's an alternative to
+C<ExtUtils::MakeMaker> to build and install perl modules.
=item *
-C<Win32API::File> has been added (for Windows builds). This module
-provides low-level access to Win32 system API calls for files/dirs.
+C<Module::Load>, by Jos Boumans, has been added. It provides a single
+interface to load Perl modules and F<.pl> files.
+
+=item *
+
+C<Module::Loaded>, by Jos Boumans, has been added. It's used to mark
+modules as loaded or unloaded.
+
+=item *
+
+C<Package::Constants>, by Jos Boumans, has been added. It's a simple
+helper to list all constants declared in a given package.
+
+=item *
+
+C<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.
=back
=head1 Utility Changes
+=head2 config_data
+
+C<config_data> is a new utility that comes with C<Module::Build>. It
+provides a command-line interface to the configuration of Perl modules
+that use Module::Build's framework of configurability (that is,
+C<*::ConfigData> modules that contain local configuration information for
+their parent modules.)
+
=head1 Documentation
=head2 New manpage, perlpragma
+The L<perlpragma> manpage documents how to write one's own lexical
+pragmas in pure Perl (something that is possible starting with 5.9.4).
+
=head2 New manpage, perlreguts
+The L<perlreguts> manpage, courtesy of Yves Orton, describes internals of the
+Perl regular expression engine.
+
=head2 New manpage, perlunitut
+The L<perlunitut> manpage is an tutorial for programming with Unicode and
+string encodings in Perl, courtesy of Juerd Waalboer.
+
=head1 Performance Enhancements
-Constants (Nicholas)
+=head2 Memory optimisations
+
+Several internal data structures (typeglobs, GVs, CVs, formats) have been
+restructured to use less memory. (Nicholas Clark)
+
+=head2 UTF-8 cache optimisation
+
+The UTF-8 caching code is now more efficient, and used more often.
+(Nicholas Clark)
+
+=head2 Regular expressions
+
+=over 4
+
+=item Engine de-recursivised
-Regular expressions (Yves)
+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)
+
+=item 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)
+
+=item 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)
+
+B<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.
+
+=item 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)
+
+=back
+
+=head2 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)
=head1 Installation and Configuration Improvements
+=head2 Relocatable installations
+
+There is now Configure support for creating a relocatable perl tree. If
+you Configure with C<-Duserelocatableinc>, then the paths in @INC (and
+everything else in %Config) can be optionally located via the path of the
+perl executable.
+
+That means that, if the string C<".../"> is found at the start of any
+path, it's substituted with the directory of $^X. So, the relocation can
+be configured on a per-directory basis, although the default with
+C<-Duserelocatableinc> is that everything is relocated. The initial
+install is done to the original configured prefix.
+
=head2 Ports
+Many improvements have been made towards making Perl work correctly on
+z/OS.
+
Perl has been reported to work on DragonFlyBSD.
=head2 Compilation improvements
All F<ppport.h> files in the XS modules bundled with perl are now
-autogenerated at build time.
+autogenerated at build time. (Marcus Holland-Moritz)
=head2 New probes
-The configuration process now detects whether strlcat and strlcpy are
+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 uses them.
+interpreter now use them. (Steve Peters)
+
+=head2 Windows build improvements
+
+=over 4
+
+=item 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)
+
+=item Support for 64-bit compiler
+
+Support for building perl with Microsoft's 64-bit compiler has been
+improved. (ActiveState)
+
+=back
=head1 Selected Bug Fixes
+=head2 PERL5SHELL and tainting
+
+On Windows, the PERL5SHELL environment variable is now checked for
+taintedness. (Rafael Garcia-Suarez)
+
+=head2 Using *FILE{IO}
+
+C<stat()> and C<-X> filetests now treat *FILE{IO} filehandles like *FILE
+filehandles. (Steve Peters)
+
+=head2 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)
+
+=head2 Overloading and UTF-8
+
+A few bugs related to UTF-8 handling with objects that have
+stringification overloaded have been fixed. (Nicholas Clark)
+
+=head2 eval memory leaks fixed
+
+Traditionally, C<eval 'syntax error'> has leaked badly. Many (but not all)
+of these leaks have now been eliminated or reduced. (Dave Mitchell)
+
+=head2 Random device on Windows
+
+In previous versions, perl would read the file F</dev/urandom> if it
+existed when seeding its random number generator. That file is unlikely
+to exist on Windows, and if it did would probably not contain appropriate
+data, so perl no longer tries to read it on Windows. (Alex Davies)
+
=head1 New or Changed Diagnostics
+=over 4
+
+=item State variable %s will be reinitialized
+
+One can assign initial values to state variables, but not when they're
+declared as a sub-part of a list assignment. See L<perldiag>.
+
+=back
+
=head1 Changed Internals
-Arenas
+A new file, F<mathoms.c>, contains functions that aren't used anymore in
+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.
-Mathoms and factorizations (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.
=head1 Known Problems
-=head2 Platform Specific Problems
+One warning test (number 263 in F<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.
=head1 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://bugs.perl.org/ . There may also be
+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 B<perlbug>
https://perl5.git.perl.org / perl5.git / blobdiff