There is no use to having Perl load "both" Strict.pm and strict.pm, especially if they both end up being the same file on some filesystems. But that that's possible is a side effect of hash keys (like in %INC) being case-sensitive and file systems sometimes being case-insensitive. I can't come up with a useful use for that.

Having two modules whose names only differ in case is non-portable at least, and in my opinion could always be flagged as a potential error. But then, I avoid Perl::Critic, so I wouldn't know how to implement it.