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PERL592DELTA(1)	       Perl Programmers Reference Guide	       PERL592DELTA(1)

       perl592delta - what is new for perl v5.9.2

       This document describes differences between the 5.9.1 and the 5.9.2
       development releases. See perl590delta and perl591delta for the
       differences between 5.8.0 and 5.9.1.

Incompatible Changes
   Packing and UTF-8 strings
       The semantics of pack() and unpack() regarding UTF-8-encoded data has
       been changed. Processing is now by default character per character
       instead of byte per byte on the underlying encoding. Notably, code that
       used things like "pack("a*", $string)" to see through the encoding of
       string will now simply get back the original $string. Packed strings
       can also get upgraded during processing when you store upgraded
       characters. You can get the old behaviour by using "use bytes".

       To be consistent with pack(), the "C0" in unpack() templates indicates
       that the data is to be processed in character mode, i.e. character by
       character; on the contrary, "U0" in unpack() indicates UTF-8 mode,
       where the packed string is processed in its UTF-8-encoded Unicode form
       on a byte by byte basis. This is reversed with regard to perl 5.8.X.

       Moreover, "C0" and "U0" can also be used in pack() templates to specify
       respectively character and byte modes.

       "C0" and "U0" in the middle of a pack or unpack format now switch to
       the specified encoding mode, honoring parens grouping. Previously,
       parens were ignored.

       Also, there is a new pack() character format, "W", which is intended to
       replace the old "C". "C" is kept for unsigned chars coded as bytes in
       the strings internal representation. "W" represents unsigned (logical)
       character values, which can be greater than 255. It is therefore more
       robust when dealing with potentially UTF-8-encoded data (as "C" will
       wrap values outside the range 0..255, and not respect the string

       In practice, that means that pack formats are now encoding-neutral,
       except "C".

       For consistency, "A" in unpack() format now trims all Unicode
       whitespace from the end of the string. Before perl 5.9.2, it used to
       strip only the classical ASCII space characters.

       The internal dump output has been improved, so that non-printable
       characters such as newline and backspace are output in "\x" notation,
       rather than octal.

       The -C option can no longer be used on the "#!" line. It wasn't working
       there anyway.

Core Enhancements
   Malloc wrapping
       Perl can now be built to detect attempts to assign pathologically large
       chunks of memory.  Previously such assignments would suffer from
       integer wrap-around during size calculations causing a misallocation,
       which would crash perl, and could theoretically be used for "stack
       smashing" attacks.  The wrapping defaults to enabled on platforms where
       we know it works (most AIX configurations, BSDi, Darwin, DEC OSF/1,
       FreeBSD, HP-UX, GNU Linux, OpenBSD, Solaris, VMS and most Win32
       compilers) and defaults to disabled on other platforms.

   Unicode Character Database 4.0.1
       The copy of the Unicode Character Database included in Perl 5.9 has
       been updated to 4.0.1 from 4.0.0.

   suidperl less insecure
       Paul Szabo has analysed and patched "suidperl" to remove existing known
       insecurities. Currently there are no known holes in "suidperl", but
       previous experience shows that we cannot be confident that these were
       the last. You may no longer invoke the set uid perl directly, so to
       preserve backwards compatibility with scripts that invoke
       #!/usr/bin/suidperl the only set uid binary is now "sperl5.9."n
       ("sperl5.9.2" for this release). "suidperl" is installed as a hard link
       to "perl"; both "suidperl" and "perl" will invoke "sperl5.9.2"
       automatically the set uid binary, so this change should be completely

       For new projects the core perl team would strongly recommend that you
       use dedicated, single purpose security tools such as "sudo" in
       preference to "suidperl".

       The "PERLIO_DEBUG" environment variable has no longer any effect for
       setuid scripts and for scripts run with -T.

       Moreover, with a thread-enabled perl, using "PERLIO_DEBUG" could lead
       to an internal buffer overflow. This has been fixed.

       In addition to bug fixes, "format"'s features have been enhanced. See

   Unicode Character Classes
       Perl's regular expression engine now contains support for matching on
       the intersection of two Unicode character classes. You can also now
       refer to user-defined character classes from within other user defined
       character classes.

   Byte-order modifiers for pack() and unpack()
       There are two new byte-order modifiers, ">" (big-endian) and "<"
       (little-endian), that can be appended to most pack() and unpack()
       template characters and groups to force a certain byte-order for that
       type or group.  See "pack" in perlfunc and perlpacktut for details.

   Byte count feature in pack()
       A new pack() template character, ".", returns the number of characters
       read so far.

   New variables
       A new variable, ${^RE_DEBUG_FLAGS}, controls what debug flags are in
       effect for the regular expression engine when running under "use re
       "debug"". See re for details.

       A new variable ${^UTF8LOCALE} indicates where an UTF-8 locale was
       detected by perl at startup.

Modules and Pragmata
   New modules
       ·   "encoding::warnings", by Audrey Tang, is a module to emit warnings
	   whenever an ASCII character string containing high-bit bytes is
	   implicitly converted into UTF-8.

       ·   "Module::CoreList", by Richard Clamp, is a small handy module that
	   tells you what versions of core modules ship with any versions of
	   Perl 5. It comes with a command-line frontend, "corelist".

   Updated And Improved Modules and Pragmata
       Dual-lived modules have been updated to be kept up-to-date with respect
       to CPAN.

       The dual-lived modules which contain an "_" in their version number are
       actually ahead of the corresponding CPAN release.

	   "B::Concise" was significantly improved.

	   There is experimental support for Linux abstract Unix domain

	   "syslog()" can now use numeric constants for facility names and
	   priorities, in addition to strings.

	   Detached threads are now also supported on Windows.

Utility Changes
       ·   The "corelist" utility is now installed with perl (see "New
	   modules" above).

       ·   "h2ph" and "h2xs" have been made a bit more robust with regard to
	   "modern" C code.

       ·   Several bugs have been fixed in "find2perl", regarding "-exec" and
	   "-eval". Also the options "-path", "-ipath" and "-iname" have been

       ·   The Perl debugger can now save all debugger commands for sourcing
	   later; notably, it can now emulate stepping backwards, by
	   restarting and rerunning all bar the last command from a saved
	   command history.

	   It can also display the parent inheritance tree of a given class.

	   Perl has a new -dt command-line flag, which enables threads support
	   in the debugger.

Performance Enhancements
       ·   Unicode case mappings ("/i", "lc", "uc", etc) are faster.

       ·   "@a = sort @a" was optimized to do in-place sort. Likewise,
	   "reverse sort ..." is now optimized to sort in reverse, avoiding
	   the generation of a temporary intermediate list.

       ·   Unnecessary assignments are optimised away in

	     my $s = undef;
	     my @a = ();
	     my %h = ();

       ·   "map" in scalar context is now optimized.

       ·   The regexp engine now implements the trie optimization : it's able
	   to factorize common prefixes and suffixes in regular expressions. A
	   new special variable, ${^RE_TRIE_MAXBUF}, has been added to fine-
	   tune this optimization.

Installation and Configuration Improvements
       Run-time customization of @INC can be enabled by passing the
       "-Dusesitecustomize" flag to configure. When enabled, this will make
       perl run $sitelibexp/ before anything else.  This
       script can then be set up to add additional entries to @INC.

       There is alpha support for relocatable @INC entries.

       Perl should build on Interix and on GNU/kFreeBSD.

Selected Bug Fixes
       Most of those bugs were reported in the perl 5.8.x maintenance track.
       Notably, quite a few utf8 bugs were fixed, and several memory leaks
       were suppressed. The perl58Xdelta manpages have more details on them.

       Development-only bug fixes include :

       $Foo::_ was wrongly forced as $main::_.

New or Changed Diagnostics
       A new warning, "!=~ should be !~", is emitted to prevent this
       misspelling of the non-matching operator.

       The warning Newline in left-justified string has been removed.

       The error Too late for "-T" option has been reformulated to be more

       There is a new compilation error, Illegal declaration of subroutine,
       for an obscure case of syntax errors.

       The diagnostic output of Carp has been changed slightly, to add a space
       after the comma between arguments. This makes it much easier for tools
       such as web browsers to wrap it, but might confuse any automatic tools
       which perform detailed parsing of Carp output.

       "perl -V" has several improvements, making it more useable from shell
       scripts to get the value of configuration variables. See perlrun for

Changed Internals
       The perl core has been refactored and reorganised in several places.
       In short, this release will not be binary compatible with any previous
       perl release.

Known Problems
       For threaded builds, ext/threads/shared/t/wait.t has been reported to
       fail some tests on HP-UX 10.20.

       Net::Ping might fail some tests on HP-UX 11.00 with the latest OS

       t/io/dup.t, t/io/open.t and lib/ExtUtils/t/Constant.t fail some tests
       on some BSD flavours.

Plans for the next release
       The current plan for perl 5.9.3 is to add CPANPLUS as a core module.
       More regular expression optimizations are also in the works.

       It is planned to release a development version of perl more frequently,
       i.e. each time something major changes.

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 v5.10.1			  2009-02-12		       PERL592DELTA(1)

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