Currently, cpanm is defaulting to installing things in a place where, by default, Perl won't find them. In my environment, the default settings for the two systems are incompatible.

I don't understand how/why that has come about, and so I'm not sure how best I should fix it.

One option is to configure one tool to match the expectations of the other -- to (everywhere) tell Perl to look where cpanm is putting things, or to tell cpanm to put things where Perl expects.

The alternative is to make the environment these tools are operating in one in which their default behaviours are compatible.

It's not obvious to me which is better -- which will maximise the number of things that "just work".