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PERL595DELTA(1)	       Perl Programmers Reference Guide	       PERL595DELTA(1)

       perl595delta - what is new for perl v5.9.5

       This document describes differences between the 5.9.4 and the 5.9.5
       development releases. See perl590delta, perl591delta, perl592delta,
       perl593delta and perl594delta for the differences between 5.8.0 and

Incompatible Changes
   Tainting and printf
       When perl is run under taint mode, "printf()" and "sprintf()" will now
       reject any tainted format argument. (Rafael Garcia-Suarez)

   undef and signal handlers
       Undefining or deleting a signal handler via "undef $SIG{FOO}" is now
       equivalent to setting it to 'DEFAULT'. (Rafael)

   strictures and array/hash dereferencing in defined()
       "defined @$foo" and "defined %$bar" are now subject to "strict 'refs'"
       (that is, $foo and $bar shall be proper references there.)  (Nicholas

       (However, "defined(@foo)" and "defined(%bar)" are discouraged
       constructs anyway.)

   "(?p{})" has been removed
       The regular expression construct "(?p{})", which was deprecated in perl
       5.8, has been removed. Use "(??{})" instead. (Rafael)

   Pseudo-hashes have been removed
       Support for pseudo-hashes has been removed from Perl 5.9. (The "fields"
       pragma remains here, but uses an alternate implementation.)

   Removal of the bytecode compiler and of perlcc
       "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).

   Removal of the JPL
       The JPL (Java-Perl Linguo) has been removed from the perl sources

   Recursive inheritance detected earlier
       Perl will now immediately throw an exception if you modify any
       package's @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
       "$foo->isa($bar)" lookup.

Core Enhancements
   Regular expressions
       Recursive Patterns
	   It is now possible to write recursive patterns without using the
	   "(??{})" 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 "(?PARNO)" syntax ("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

	   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)

       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
	   "(?<NAME>....)".  It's possible to backreference to a named buffer
	   with the "\k<NAME>" syntax. In code, the new magical hashes "%+"
	   and "%-" can be used to access the contents of the capture buffers.

	   Thus, to replace all doubled chars, one could write


	   Only buffers with defined contents will be "visible" in the "%+"
	   hash, so it's possible to do something like

	       foreach my $name (keys %+) {
		   print "content of buffer '$name' is $+{$name}\n";

	   The "%-" 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.

	   "%+" and "%-" are implemented as tied hashes through the new module

	   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


	   $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)

       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 "?+",
	   "*+", "++", "{min,max}+" are now legal quantifiers. (Yves Orton)

       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 perlre for their descriptions. (Yves

       Relative backreferences
	   A new syntax "\g{N}" or "\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 "Capture buffers"
	   in perlre. (Yves Orton)

       "\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 "\K" as a way to do something like floating length
	   positive lookbehind. It is also useful in substitutions like:


	   that can now be converted to


	   which is much more efficient. (Yves Orton)

       Vertical and horizontal whitespace, and linebreak
	   Regular expressions now recognize the "\v" and "\h" escapes, that
	   match vertical and horizontal whitespace, respectively. "\V" and
	   "\H" logically match their complements.

	   "\R" matches a generic linebreak, that is, vertical whitespace,
	   plus the multi-character sequence "\x0D\x0A".

   The "_" prototype
       A new prototype character has been added. "_" is equivalent to "$" (it
       denotes a scalar), but defaults to $_ 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 "_" for some built-ins in appropriate cases
       (for example, "prototype('CORE::rmdir')"). (Rafael)

   UNITCHECK blocks
       "UNITCHECK", a new special code block has been introduced, in addition
       to "BEGIN", "CHECK", "INIT" and "END".

       "CHECK" and "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, "UNITCHECK" blocks are executed
       just after the unit which defined them has been compiled. See perlmod
       for more information. (Alex Gough)

   readpipe() is now overridable
       The built-in function readpipe() is now overridable. Overriding it
       permits also to override its operator counterpart, "qx//" (a.k.a.
       "``").  Moreover, it now defaults to $_ if no argument is provided.

   default argument for readline()
       readline() now defaults to *ARGV if no argument is provided. (Rafael)

   UCD 5.0.0
       The copy of the Unicode Character Database included in Perl 5.9 has
       been updated to version 5.0.0.

   Smart match
       The smart match operator ("~~") is now available by default (you don't
       need to enable it with "use feature" any longer). (Michael G Schwern)

   Implicit loading of "feature"
       The "feature" pragma is now implicitly loaded when you require a
       minimal perl version (with the "use VERSION" construct) greater than,
       or equal to, 5.9.5.

Modules and Pragmas
   New Pragma, "mro"
       A new pragma, "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 multiple inheritance hierarchy.
       The default MRO hasn't changed (DFS, for Depth First Search). Another
       MRO is available: the C3 algorithm. See mro for more information.
       (Brandon Black)

       Note that, due to changes in the implementation of class hierarchy
       search, code that used to undef the *ISA glob will most probably break.
       Anyway, undef'ing *ISA had the side-effect of removing the magic on the
       @ISA array and should not have been done in the first place.

   bignum, bigint, bigrat
       The three numeric pragmas "bignum", "bigint" and "bigrat" are now
       lexically scoped. (Tels)

       Many bugs have been fixed; noteworthy are comparisons with NaN, which
       no longer warn about undef values.

       The following things are new:

	   The config() method now also supports the calling-style
	   "config('lib')" in addition to "config()->{'lib'}".

	   Upon import, using "lib => 'Foo'" now warns if the low-level
	   library cannot be found. To suppress the warning, you can use "try
	   => 'Foo'" instead. To convert the warning into a die, use "only =>
	   'Foo'" instead.

       roundmode common
	   A rounding mode of "common" is now supported.

       Also, support for the following methods has been added:

       bpi(), bcos(), bsin(), batan(), batan2()
       bexp(), bnok()
       from_hex(), from_oct(), and from_bin()

       In addition, the default math-backend (Calc (Perl) and FastCalc (XS))
       now support storing numbers in parts with 9 digits instead of 7 on
       Perls with either 64bit integer or long double support. This means math
       operations scale better and are thus faster for really big numbers.

   New Core Modules
       ·   "Locale::Maketext::Simple", needed by CPANPLUS, is a simple wrapper
	   around "Locale::Maketext::Lexicon". Note that
	   "Locale::Maketext::Lexicon" isn't included in the perl core; the
	   behaviour of "Locale::Maketext::Simple" gracefully degrades when
	   the later isn't present.

       ·   "Params::Check" implements a generic input parsing/checking
	   mechanism. It is used by CPANPLUS.

       ·   "Term::UI" simplifies the task to ask questions at a terminal

       ·   "Object::Accessor" provides an interface to create per-object

       ·   "Module::Pluggable" is a simple framework to create modules that
	   accept pluggable sub-modules.

       ·   "Module::Load::Conditional" provides simple ways to query and
	   possibly load installed modules.

       ·   "Time::Piece" provides an object oriented interface to time
	   functions, overriding the built-ins localtime() and gmtime().

       ·   "IPC::Cmd" helps to find and run external commands, possibly

       ·   "File::Fetch" provide a simple generic file fetching mechanism.

       ·   "Log::Message" and "Log::Message::Simple" are used by the log
	   facility of "CPANPLUS".

       ·   "Archive::Extract" is a generic archive extraction mechanism for
	   .tar (plain, gziped or bzipped) or .zip files.

       ·   "CPANPLUS" provides an API and a command-line tool to access the
	   CPAN mirrors.

   Module changes
	   The "assertions" pragma, its submodules "assertions::activate" and
	   "assertions::compat" and the -A command-line switch have been
	   removed.  The interface was not judged mature enough for inclusion
	   in a stable release.

	   The "base" pragma now warns if a class tries to inherit from
	   itself.  (Curtis "Ovid" Poe)

       "strict" and "warnings"
	   "strict" and "warnings" will now complain loudly if they are loaded
	   via incorrect casing (as in "use Strict;"). (Johan Vromans)

	   The "warnings" pragma doesn't load "Carp" anymore. That means that
	   code that used "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";

	   "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
	   less for more. (Joshua ben Jore)

	   "Attribute::Handlers" can now report the caller's file and line
	   number.  (David Feldman)

	   "B::Lint" is now based on "Module::Pluggable", and so can be
	   extended with plugins. (Joshua ben Jore)

       "B" It's now possible to access the lexical pragma hints ("%^H") by
	   using the method B::COP::hints_hash(). It returns a "B::RHE"
	   object, which in turn can be used to get a hash reference via the
	   method B::RHE::HASH(). (Joshua ben Jore)

	   As the old 5005thread threading model has been removed, in favor of
	   the ithreads scheme, the "Thread" module is now a compatibility
	   wrapper, to be used in old code only. It has been removed from the
	   default list of dynamic extensions.

Utility Changes
       "cpanp", the CPANPLUS shell, has been added. ("cpanp-run-perl", an
       helper for CPANPLUS operation, has been added too, but isn't intended
       for direct use).

       "cpan2dist" is a new utility, that comes with CPANPLUS. It's a tool to
       create distributions (or packages) from CPAN modules.

       The output of "pod2html" has been enhanced to be more customizable via
       CSS. Some formatting problems were also corrected. (Jari Aalto)

   New manpage, perlunifaq
       A new manual page, perlunifaq (the Perl Unicode FAQ), has been added
       (Juerd Waalboer).

Installation and Configuration Improvements
   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.)

   Visual C++
       Perl now can be compiled with Microsoft Visual C++ 2005.

   Static build on Win32
       It's now possible to build a "perl-static.exe" that doesn't depend on
       "perl59.dll" on Win32. See the Win32 makefiles for details.  (Vadim

   win32 builds
       All win32 builds (MS-Win, WinCE) have been merged and cleaned up.

   "d_pseudofork" and "d_printf_format_null"
       A new configuration variable, available as $Config{d_pseudofork} in the
       Config module, has been added, to distinguish real fork() support from
       fake pseudofork used on Windows platforms.

       A new configuration variable, "d_printf_format_null", has been added,
       to see if printf-like formats are allowed to be NULL.

       "Configure -h" has been extended with the most used option.

       Much less 'Whoa there' messages.

   64bit systems
       Better detection of 64bit(only) systems, and setting all the (library)
       paths accordingly.

       Perl has been reported to work on MidnightBSD.

       Support for Cray XT4 Catamount/Qk has been added.

       Vendor patches have been merged for RedHat and GenToo.

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

       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 "Deferred
       Signals (Safe Signals)" in perlipc). (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 "-w" and "-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 ":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 if the variable was changed while the local() was in
       effect (as in "local $h{$x}; ++$x"). (Bo Lindbergh)

New or Changed Diagnostics
       Two deprecation warnings have been added: (Rafael)

	   Opening dirhandle %s also as a file
	   Opening filehandle %s also as a directory

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

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 .  There may also be information at , 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 to be analysed by
       the Perl porting team.

       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 v5.12.2			  2010-09-05		       PERL595DELTA(1)
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