libtask-weaken-perl

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 necessarily 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.