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Finding out exactly what CPAN distributions you have installed, including exactly what versions of those distributions, is remarkably tricky.
In this talk I'll show a new utility that leverages metacpan to help it perform this task accurately. It'll even pinpoint remnant files and files that have local modifications.
This utility makes it possible to 'clone' a perl library tree by reinstalling the distributions into a different directory tree. That's very handy when moving between major perl versions where extensions need to be recompiled. The list of specific distributions it generates can be used with carton.
This kind of cloning has the added benefit of re-testing all the specific distribution versions that are being used against all the specific prerequisite versions that are being used. It's surprising how often this re-testing finds problems.