CPAN handling
Later the same week I was having problems building a Python package, I rounded out my fun by having problems building a Perl package.
I learned that <prefix>/perl/<version>/Config.pm includes the various flags and settings that your perl was built with, and can be your guide to how to build things to play nice with your Perl instance. (Module::Build tries to do this automagically, but it wasn't working with the idiosyncrasies of the environment I was working with.)