=head1 Incompatible Changes
+=head2 Tainting and printf
+
+When perl is run under taint mode, C<printf()> and C<sprintf()> will now
+reject any tainted format argument. (Rafael Garcia-Suarez)
+
+=head2 undef and signal handlers
+
+Undefining or deleting a signal handler via C<undef $SIG{FOO}> is now
+equivalent to setting it to C<'DEFAULT'>. (Rafael)
+
+=head2 strictures and array/hash dereferencing in defined()
+
+C<defined @$foo> and C<defined %$bar> are now subject to C<strict 'refs'>
+(that is, C<$foo> and C<$bar> shall be proper references there.)
+(Nicholas Clark)
+
+(However, C<defined(@foo)> and C<defined(%bar)> are discouraged constructs
+anyway.)
+
+=head2 C<(?p{})> has been removed
+
+The regular expression construct C<(?p{})>, which was deprecated in perl
+5.8, has been removed. Use C<(??{})> instead. (Rafael)
+
+=head2 Removal of the bytecode compiler and of perlcc
+
+C<perlcc>, the byteloader and the supporting modules (B::C, B::CC,
+B::Bytecode, etc.) are no longer distributed with the perl sources. Those
+experimental tools have never worked reliably, and, due to the lack of
+volunteers to keep them in line with the perl interpreter developments, it
+was decided to remove them instead of shipping a broken version of those.
+The last version of those modules can be found with perl 5.9.4.
+
+However the B compiler framework stays supported in the perl core, as with
+the more useful modules it has permitted (among others, B::Deparse and
+B::Concise).
+
+=head2 Removal of the JPL
+
+The JPL (Java-Perl Linguo) has been removed from the perl sources tarball.
+
+=head2 Recursive inheritance detected earlier
+
+Perl will now immediately throw an exception if you modify any package's
+C<@ISA> in such a way that it would cause recursive inheritance.
+
+Previously, the exception would not occur until Perl attempted to make
+use of the recursive inheritance while resolving a method or doing a
+C<$foo-E<gt>isa($bar)> lookup.
+
=head1 Core Enhancements
+=head2 Regular expressions
+
+=over 4
+
+=item Recursive Patterns
+
+It is now possible to write recursive patterns without using the C<(??{})>
+construct. This new way is more efficient, and in many cases easier to
+read.
+
+Each capturing parenthesis can now be treated as an independent pattern
+that can be entered by using the C<(?PARNO)> syntax (C<PARNO> standing for
+"parenthesis number"). For example, the following pattern will match
+nested balanced angle brackets:
+
+ /
+ ^ # start of line
+ ( # start capture buffer 1
+ < # match an opening angle bracket
+ (?: # match one of:
+ (?> # don't backtrack over the inside of this group
+ [^<>]+ # one or more non angle brackets
+ ) # end non backtracking group
+ | # ... or ...
+ (?1) # recurse to bracket 1 and try it again
+ )* # 0 or more times.
+ > # match a closing angle bracket
+ ) # end capture buffer one
+ $ # end of line
+ /x
+
+Note, users experienced with PCRE will find that the Perl implementation
+of this feature differs from the PCRE one in that it is possible to
+backtrack into a recursed pattern, whereas in PCRE the recursion is
+atomic or "possessive" in nature. (Yves Orton)
+
+=item Named Capture Buffers
+
+It is now possible to name capturing parenthesis in a pattern and refer to
+the captured contents by name. The naming syntax is C<< (?<NAME>....) >>.
+It's possible to backreference to a named buffer with the C<< \k<NAME> >>
+syntax. In code, the new magical hashes C<%+> and C<%-> can be used to
+access the contents of the capture buffers.
+
+Thus, to replace all doubled chars, one could write
+
+ s/(?<letter>.)\k<letter>/$+{letter}/g
+
+Only buffers with defined contents will be "visible" in the C<%+> hash, so
+it's possible to do something like
+
+ foreach my $name (keys %+) {
+ print "content of buffer '$name' is $+{$name}\n";
+ }
+
+The C<%-> hash is a bit more complete, since it will contain array refs
+holding values from all capture buffers similarly named, if there should
+be many of them.
+
+C<%+> and C<%-> are implemented as tied hashes through the new module
+C<Tie::Hash::NamedCapture>.
+
+Users exposed to the .NET regex engine will find that the perl
+implementation differs in that the numerical ordering of the buffers
+is sequential, and not "unnamed first, then named". Thus in the pattern
+
+ /(A)(?<B>B)(C)(?<D>D)/
+
+$1 will be 'A', $2 will be 'B', $3 will be 'C' and $4 will be 'D' and not
+$1 is 'A', $2 is 'C' and $3 is 'B' and $4 is 'D' that a .NET programmer
+would expect. This is considered a feature. :-) (Yves Orton)
+
+=item Possessive Quantifiers
+
+Perl now supports the "possessive quantifier" syntax of the "atomic match"
+pattern. Basically a possessive quantifier matches as much as it can and never
+gives any back. Thus it can be used to control backtracking. The syntax is
+similar to non-greedy matching, except instead of using a '?' as the modifier
+the '+' is used. Thus C<?+>, C<*+>, C<++>, C<{min,max}+> are now legal
+quantifiers. (Yves Orton)
+
+=item Backtracking control verbs
+
+The regex engine now supports a number of special-purpose backtrack
+control verbs: (*THEN), (*PRUNE), (*MARK), (*SKIP), (*COMMIT), (*FAIL)
+and (*ACCEPT). See L<perlre> for their descriptions. (Yves Orton)
+
+=item Relative backreferences
+
+A new syntax C<\g{N}> or C<\gN> where "N" is a decimal integer allows a
+safer form of back-reference notation as well as allowing relative
+backreferences. This should make it easier to generate and embed patterns
+that contain backreferences. See L<perlre/"Capture buffers">. (Yves Orton)
+
+=item C<\K> escape
+
+The functionality of Jeff Pinyan's module Regexp::Keep has been added to
+the core. You can now use in regular expressions the special escape C<\K>
+as a way to do something like floating length positive lookbehind. It is
+also useful in substitutions like:
+
+ s/(foo)bar/$1/g
+
+that can now be converted to
+
+ s/foo\Kbar//g
+
+which is much more efficient. (Yves Orton)
+
+=item Vertical and horizontal whitespace, and linebreak
+
+Regular expressions now recognize the C<\v> and C<\h> escapes, that match
+vertical and horizontal whitespace, respectively. C<\V> and C<\H>
+logically match their complements.
+
+C<\R> matches a generic linebreak, that is, vertical whitespace, plus
+the multi-character sequence C<"\x0D\x0A">.
+
+=back
+
+=head2 The C<_> prototype
+
+A new prototype character has been added. C<_> is equivalent to C<$> (it
+denotes a scalar), but defaults to C<$_> if the corresponding argument
+isn't supplied. Due to the optional nature of the argument, you can only
+use it at the end of a prototype, or before a semicolon.
+
+This has a small incompatible consequence: the prototype() function has
+been adjusted to return C<_> for some built-ins in appropriate cases (for
+example, C<prototype('CORE::rmdir')>). (Rafael)
+
+=head2 UNITCHECK blocks
+
+C<UNITCHECK>, a new special code block has been introduced, in addition to
+C<BEGIN>, C<CHECK>, C<INIT> and C<END>.
+
+C<CHECK> and C<INIT> blocks, while useful for some specialized purposes,
+are always executed at the transition between the compilation and the
+execution of the main program, and thus are useless whenever code is
+loaded at runtime. On the other hand, C<UNITCHECK> blocks are executed
+just after the unit which defined them has been compiled. See L<perlmod>
+for more information. (Alex Gough)
+
+=head2 readpipe() is now overridable
+
+The built-in function readpipe() is now overridable. Overriding it permits
+also to override its operator counterpart, C<qx//> (a.k.a. C<``>).
+Moreover, it now defaults to C<$_> if no argument is provided. (Rafael)
+
+=head2 default argument for readline()
+
+readline() now defaults to C<*ARGV> if no argument is provided. (Rafael)
+
+=head2 UCD 5.0.0
+
+The copy of the Unicode Character Database included in Perl 5.9 has
+been updated to version 5.0.0.
+
+=head2 Smart match
+
+The smart match operator (C<~~>) is now available by default (you don't
+need to enable it with C<use feature> any longer). (Michael G Schwern)
+
+=head2 Implicit loading of C<feature>
+
+The C<feature> pragma is now implicitly loaded when you require a minimal
+perl version (with the C<use VERSION> construct) greater than, or equal
+to, 5.9.5.
+
=head1 Modules and Pragmas
+=head2 New Pragma, C<mro>
+
+A new pragma, C<mro> (for Method Resolution Order) has been added. It
+permits to switch, on a per-class basis, the algorithm that perl uses to
+find inherited methods in case of a mutiple inheritance hierachy. The
+default MRO hasn't changed (DFS, for Depth First Search). Another MRO is
+available: the C3 algorithm. See L<mro> for more information.
+(Brandon Black)
+
+=head2 bignum, bigint, bigrat
+
+The three numeric pragmas C<bignum>, C<bigint> and C<bigrat> are now
+lexically scoped. (Tels)
+
=head2 New Core Modules
+=over 4
+
+=item *
+
+C<Locale::Maketext::Simple>, needed by CPANPLUS, is a simple wrapper around
+C<Locale::Maketext::Lexicon>. Note that C<Locale::Maketext::Lexicon> isn't
+included in the perl core; the behaviour of C<Locale::Maketext::Simple>
+gracefully degrades when the later isn't present.
+
+=item *
+
+C<Params::Check> implements a generic input parsing/checking mechanism. It
+is used by CPANPLUS.
+
+=item *
+
+C<Term::UI> simplifies the task to ask questions at a terminal prompt.
+
+=item *
+
+C<Object::Accessor> provides an interface to create per-object accessors.
+
+=item *
+
+C<Module::Pluggable> is a simple framework to create modules that accept
+pluggable sub-modules.
+
+=item *
+
+C<Module::Load::Conditional> provides simple ways to query and possibly
+load installed modules.
+
+=item *
+
+C<Time::Piece> provides an object oriented interface to time functions,
+overriding the built-ins localtime() and gmtime().
+
+=item *
+
+C<IPC::Cmd> helps to find and run external commands, possibly
+interactively.
+
+=item *
+
+C<File::Fetch> provide a simple generic file fetching mechanism.
+
+=item *
+
+C<Archive::Extract> is a generic archive extraction mechanism
+for F<.tar> (plain, gziped or bzipped) or F<.zip> files.
+
+=item *
+
+C<CPANPLUS> provides an API and a command-line tool to access the CPAN
+mirrors.
+
+=back
+
+=head2 Module changes
+
+=over 4
+
+=item C<base>
+
+The C<base> pragma now warns if a class tries to inherit from itself.
+(Curtis "Ovid" Poe)
+
+=item C<strict> and C<warnings>
+
+C<strict> and C<warnings> will now complain loudly if they are loaded via
+incorrect casing (as in C<use Strict;>). (Johan Vromans)
+
+=item C<warnings>
+
+The C<warnings> pragma doesn't load C<Carp> anymore. That means that code
+that used C<Carp> routines without having loaded it at compile time might
+need to be adjusted; typically, the following (faulty) code won't work
+anymore, and will require parentheses to be added after the function name:
+
+ use warnings;
+ require Carp;
+ Carp::confess "argh";
+
+=item C<less>
+
+C<less> now does something useful (or at least it tries to). In fact, it
+has been turned into a lexical pragma. So, in your modules, you can now
+test whether your users have requested to use less CPU, or less memory,
+less magic, or maybe even less fat. See L<less> for more. (Joshua ben
+Jore)
+
+=item C<Attribute::Handlers>
+
+C<Attribute::Handlers> can now report the caller's file and line number.
+(David Feldman)
+
+=item C<B::Lint>
+
+C<B::Lint> is now based on C<Module::Pluggable>, and so can be extended
+with plugins. (Joshua ben Jore)
+
+=item C<B>
+
+It's now possible to access the lexical pragma hints (C<%^H>) by using the
+method B::COP::hints_hash(). It returns a C<B::RHE> object, which in turn
+can be used to get a hash reference via the method B::RHE::HASH(). (Joshua
+ben Jore)
+
+=for p5p XXX document this in B.pm too
+
+=item C<Thread>
+
+As the old 5005thread threading model has been removed, in favor of the
+ithreads scheme, the C<Thread> module is now a compatibility wrapper, to
+be used in old code only.
+
+=back
+
=head1 Utility Changes
+=head2 C<cpanp>
+
+C<cpanp>, the CPANPLUS shell, has been added. (C<cpanp-run-perl>, an
+helper for CPANPLUS operation, has been added too, but isn't intended for
+direct use).
+
+=head2 C<cpan2dist>
+
+C<cpan2dist> is a new utility, that comes with CPANPLUS. It's a tool to
+create distributions (or packages) from CPAN modules.
+
+=head2 C<pod2html>
+
+The output of C<pod2html> has been enhanced to be more customizable via
+CSS. Some formatting problems were also corrected. (Jari Aalto)
+
=head1 Documentation
+=head2 New manpage, perlunifaq
+
+A new manual page, L<perlunifaq> (the Perl Unicode FAQ), has been added
+(Juerd Waalboer).
+
=head1 Performance Enhancements
=head1 Installation and Configuration Improvements
+=head2 C++ compatibility
+
+Efforts have been made to make perl and the core XS modules compilable
+with various C++ compilers (although the situation is not perfect with
+some of the compilers on some of the platforms tested.)
+
+=head2 Visual C++
+
+Perl now can be compiled with Microsoft Visual C++ 2005.
+
+=head2 Static build on Win32
+
+It's now possible to build a C<perl-static.exe> that doesn't depend
+on C<perl59.dll> on Win32. See the Win32 makefiles for details.
+(Vadim Konovalov)
+
+=head2 C<d_pseudofork>
+
+A new configuration variable, available as C<$Config{d_pseudofork}> in
+the L<Config> module, has been added, to distinguish real fork() support
+from fake pseudofork used on Windows platforms.
+
+=head2 Ports
+
+Perl has been reported to work on MidnightBSD.
+
=head1 Selected Bug Fixes
+PerlIO::scalar will now prevent writing to read-only scalars. Moreover,
+seek() is now supported with PerlIO::scalar-based filehandles, the
+underlying string being zero-filled as needed. (Rafael, Jarkko Hietaniemi)
+
+study() never worked for UTF-8 strings, but could lead to false results.
+It's now a no-op on UTF-8 data. (Yves Orton)
+
+The signals SIGILL, SIGBUS and SIGSEGV are now always delivered in an
+"unsafe" manner (contrary to other signals, that are deferred until the
+perl interpreter reaches a reasonably stable state; see
+L<perlipc/"Deferred Signals (Safe Signals)">). (Rafael)
+
+When a module or a file is loaded through an @INC-hook, and when this hook
+has set a filename entry in %INC, __FILE__ is now set for this module
+accordingly to the contents of that %INC entry. (Rafael)
+
+The C<-w> and C<-t> switches can now be used together without messing
+up what categories of warnings are activated or not. (Rafael)
+
+Duping a filehandle which has the C<:utf8> PerlIO layer set will now
+properly carry that layer on the duped filehandle. (Rafael)
+
+Localizing an hash element whose key was given as a variable didn't work
+correctly (as in C<local $h{$x}>). (Bo Lindbergh)
+
=head1 New or Changed Diagnostics
+=head2 Deprecations
+
+Two deprecation warnings have been added: (Rafael)
+
+ Opening dirhandle %s also as a file
+ Opening filehandle %s also as a directory
+
=head1 Changed Internals
+The anonymous hash and array constructors now take 1 op in the optree
+instead of 3, now that pp_anonhash and pp_anonlist return a reference to
+an hash/array when the op is flagged with OPf_SPECIAL (Nicholas Clark).
+
+=for p5p XXX have we some docs on how to create regexp engine plugins, since that's now possible ? (perlreguts)
+
+=for p5p XXX new BIND SV type, #29544, #29642
+
=head1 Known Problems
=head2 Platform Specific Problems
projects / p5sagit/p5-mst-13.2.git / blobdiff