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Source   Latest Release: perl-5.17.11


perl5177delta - what is new for perl v5.17.7


This document describes differences between the 5.17.6 release and the 5.17.7 release.

If you are upgrading from an earlier release such as 5.17.5, first read perl5176delta, which describes differences between 5.17.5 and 5.17.6.

Core Enhancements ^

$&, $` and $' are no longer slow

These three infamous variables have been redeemed and no longer slow down your program when used. Hence, the /p regular expression flag now does nothing.

Security ^

Storable security warning in documentation

The documentation for Storable now includes a section which warns readers of the danger of accepting Storable documents from untrusted sources. The short version is that deserializing certain types of data can lead to loading modules and other code execution. This is documented behavior and wanted behavior, but this opens an attack vector for malicious entities.

Locale::Maketext allowed code injection via a malicious template

If users could provide a translation string to Locale::Maketext, this could be used to invoke arbitrary Perl subroutines available in the current process.

This has been fixed, but it is still possible to invoke any method provided by Locale::Maketext itself or a subclass that you are using. One of these methods in turn will invoke the Perl core's sprintf subroutine.

In summary, allowing users to provide translation strings without auditing them is a bad idea.

This vulnerability is documented in CVE-2012-6329.

Incompatible Changes ^

readline() with $/ = \N now reads N characters, not N bytes

Previously, when reading from a stream with I/O layers such as encoding, the readline() function, otherwise known as the <> operator, would read N bytes from the top-most layer. [perl #79960]

Now, N characters are read instead.

There is no change in behaviour when reading from streams with no extra layers, since bytes map exactly to characters.

Lexical subroutine warnings have moved

The warning about the use of an experimental feature emitted when lexical subroutines (added in 5.17.4) are used now happens when the subroutine itself is declared, not when the "lexical_subs" feature is activated via use feature.

This stops use feature ':all' from warning, but causes my sub foo; my sub bar to warn twice.

Overridden glob is now passed one argument

glob overrides used to be passed a magical undocumented second argument that identified the caller. Nothing on CPAN was using this, and it got in the way of a bug fix, so it was removed. If you really need to identify the caller, see Devel::Callsite on CPAN.

Deprecations ^

Lexical $_ is now deprecated

Since it was introduced in Perl 5.10, it has caused much confusion with no obvious solution:

Various XS-callable functions are now deprecated

The following functions will be removed from a future version of Perl, and should not be used. With participating C compilers (e.g., gcc), compiling any file that uses any of these will generate a warning. These were not intended for public use; there are equivalent, faster, macros for most of them. See "Character classes" in perlapi: is_uni_ascii, is_uni_ascii_lc, is_uni_blank, is_uni_blank_lc, is_uni_cntrl, is_uni_cntrl_lc, is_uni_idfirst_lc, is_uni_space, is_uni_space_lc, is_uni_xdigit, is_uni_xdigit_lc, is_utf8_ascii, is_utf8_blank, is_utf8_cntrl, is_utf8_idcont, is_utf8_idfirst, is_utf8_perl_space, is_utf8_perl_word, is_utf8_posix_digit, is_utf8_space, is_utf8_xdigit. is_utf8_xidcont, is_utf8_xidfirst, to_uni_lower_lc, to_uni_title_lc, and to_uni_upper_lc.

Performance Enhancements ^

Modules and Pragmata ^

Updated Modules and Pragmata

Documentation ^

Changes to Existing Documentation

"Character classes" in perlapi

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

Internal Changes ^

Selected Bug Fixes ^

Known Problems ^

There may be a failure in the t/op/require_errors.t test if you run the test suite as the root user.

Acknowledgements ^

Perl 5.17.7 represents approximately 4 weeks of development since Perl 5.17.6 and contains approximately 30,000 lines of changes across 490 files from 26 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 5.17.7:

Alexandr Ciornii, Bob Ernst, Brian Carlson, Chris 'BinGOs' Williams, Craig A. Berry, Daniel Dragan, Dave Rolsky, David Mitchell, Father Chrysostomos, Hugo van der Sanden, James E Keenan, Joel Berger, Karl Williamson, Lukas Mai, Martin Hasch, Matthew Horsfall, Nicholas Clark, Ricardo Signes, Ruslan Zakirov, Sergey Alekseev, Steffen Müller, Sullivan Beck, Sven Strickroth, Sébastien Aperghis-Tramoni, Tony Cook, Yves Orton.

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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