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perl5154delta - what is new for perl v5.15.4


This document describes differences between the 5.15.3 release and the 5.15.4 release.

If you are upgrading from an earlier release such as 5.15.3, first read perl5153delta, which describes differences between 5.15.3 and 5.15.4.

Core Enhancements ^

$^X converted to an absolute path on FreeBSD, OS X and Solaris

$^X is now converted to an absolute path on OS X, FreeBSD (without needing /proc mounted) and Solaris 10 and 11. This augments the previous approach of using /proc on Linux, FreeBSD and NetBSD (in all cases, where mounted).

This makes relocatable perl installations more useful on these platforms. (See "Relocatable @INC" in INSTALL)

Unicode Symbol Names

Perl now has proper support for Unicode in symbol names. It used to be that *{$foo} would ignore the internal UTF8 flag and use the bytes of the underlying representation to look up the symbol. That meant that *{"\x{100}"} and *{"\xc4\x80"} would return the same thing. All these parts of Perl have been fixed to account for Unicode:

In addition, a parsing bug has been fixed that prevented *{é} from implicitly quoting the name, but instead interpreted it as *{+é}, which would cause a strict violation.

*{"*a::b"} automatically strips off the * if it is followed by an ASCII letter. That has been extended to all Unicode identifier characters.

is now subject to "Used only once" warnings. It used to be exempt, as it was treated as a punctuation variable.

Also, single-character Unicode punctuation variables (like $‰) are now supported [perl #69032]. They are also supported with our and my, but that is a mistake that will be fixed before 5.16.

Support for Embedded Nulls

Some parts of Perl did not work correctly with nulls (chr 0) embedded in strings. That meant that, for instance, $m = "a\0b"; foo->$m would call the "a" method, instead of the actual method name contained in $m. These parts of perl have been fixed to support nulls:

One side effect of these changes is that blessing into "\0" no longer causes ref() to return false.

Autoloaded sort Subroutines

Custom sort subroutines can now be autoloaded [perl #30661]:

    sub AUTOLOAD { ... }
    @sorted = sort foo @list; # uses AUTOLOAD

Improved typemaps for Some Builtin Types

Most XS authors will be aware that there is a longstanding bug in the OUTPUT typemap for T_AVREF (AV*), T_HVREF (HV*), T_CVREF (CV*), and T_SVREF (SVREF or \$foo) that requires manually decrementing the reference count of the return value instead of the typemap taking care of this. For backwards-compatibility, this cannot be changed in the default typemaps. But we now provide additional typemaps T_AVREF_REFCOUNT_FIXED, etc. that do not exhibit this bug. Using them in your extension is as simple as having one line in your TYPEMAP section:


Performance Enhancements ^

Modules and Pragmata ^

Updated Modules and Pragmata

Documentation ^

Changes to Existing Documentation

perlfunc, open



Diagnostics ^

The following additions or changes have been made to diagnostic output, including warnings and fatal error messages. For the complete list of diagnostic messages, see perldiag.

Changes to Existing Diagnostics

Testing ^

Internal Changes ^

Selected Bug Fixes ^

Acknowledgements ^

Perl 5.15.4 represents approximately 1 month of development since Perl 5.15.3 and contains approximately 31,000 lines of changes across 350 files from 23 authors.

Perl continues to flourish into its third decade thanks to a vibrant community of users and developers. The following people are known to have contributed the improvements that became Perl 5.15.4:

Alan Haggai Alavi, Brian Fraser, Chip Salzenberg, Chris 'BinGOs' Williams, Dave Rolsky, David Golden, David Mitchell, Dennis Kaarsemaker, Eric Brine, Father Chrysostomos, Florian Ragwitz, George Greer, Gerard Goossen, H.Merijn Brand, Jim Cromie, John P. Linderman, Karl Williamson, Nicholas Clark, Reini Urban, Steffen Müller, Stevan Little, Thorsten Glaser, Tony Cook.

The list above is almost certainly incomplete as it is automatically generated from version control history. In particular, it does not include the names of the (very much appreciated) contributors who reported issues to the Perl bug tracker.

Many of the changes included in this version originated in the CPAN modules included in Perl's core. We're grateful to the entire CPAN community for helping Perl to flourish.

For a more complete list of all of Perl's historical contributors, please see the AUTHORS file in the Perl source distribution.

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.

If the bug you are reporting has security implications, which make it inappropriate to send to a publicly archived mailing list, then please send it to This points to a closed subscription unarchived mailing list, which includes all the core committers, who will be able to help assess the impact of issues, figure out a resolution, and help co-ordinate the release of patches to mitigate or fix the problem across all platforms on which Perl is supported. Please only use this address for security issues in the Perl core, not for modules independently distributed on CPAN.


The Changes file for an explanation of how to view 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.

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