Task::Weaken(3) User Contributed Perl Documentation Task::Weaken(3)
Task::Weaken - Ensure that a platform has weaken support
One recurring problem in modules that use Scalar::Util's "weaken" function is that it is
not present in the pure-perl variant.
While this isn't necesarily always a problem in a straight CPAN-based Perl environment,
some operating system distributions only include the pure-Perl versions, don't include the
XS version, and so weaken is then "missing" from the platform, despite passing a
dependency on Scalar::Util successfully.
Most notably this is RedHat Linux at time of writing, but other come and go and do the
same thing, hence "recurring problem".
The normal solution is to manually write tests in each distribution to ensure that
"weaken" is available.
This restores the functionality testing to a dependency you do once in your Makefile.PL,
rather than something you have to write extra tests for each time you write a module.
It should also help make the package auto-generators for the various operating systems
play more nicely, because it introduces a dependency that they have to have a proper
weaken in order to work.
How this Task works
Part of the problem seems to stem from the fact that some distributions continue to
include modules even if they fail some of their tests.
To get around that for this module, it will do a few dirty tricks.
If Scalar::Util is not available at all, it will issue a normal dependency on the module.
However, if Scalar::Util is relatively new ( it is >= 1.19 ) and the module does not have
weaken, the install will bail out altogether with a long error encouraging the user to
seek support from their vendor (this problem happens most often in vendor-packaged Perl
This distribution also contains tests to ensure that weaken is available using more normal
So if your module uses "weaken", you can just add the following to your
Module::Install-based Makefile.PL (or equivalent).
requires 'Task::Weaken' => 0;
Bugs should be always be reported via the CPAN bug tracker at
For other issues,contact the author.
Adam Kennedy <email@example.com>
Task, Scalar::Util, <http://ali.as/>
Copyright 2006 - 2011 Adam Kennedy.
This program is free software; you can redistribute it and/or modify it under the same
terms as Perl itself.
The full text of the license can be found in the LICENSE file included with this module.
perl v5.16.3 2011-03-08 Task::Weaken(3)