Check the CPAN configuration.   There are variables (“such as PREFIX,” he said with the suddenly-vague expression of someone who’s had only one cup of coffee...) which influence exactly how and where CPAN tries to put things.

I have always used absolute addresses here.   In other words, figure out what "~" corresponds to (it doesn’t change...), and specify the directory explicitly.

“Okay, that’s it ... time for coffee,” he mumbled...