find lib -name '*.pm' | xargs perl -pi -e 's/.../.../'

is usually quite sufficient for purpose if you have a reasonable idea what's going on in your codebase (and if you don't, you probably don't want to be renaming things yet).

Doesn't mean a real refactoring tool such as the ones people've been playing with for http://padre.perlide.org/ wouldn't be better, but it's amazing how well a simple brute force replace works on a reasonably tested codebase.

Might work for classes. Good luck with "count" or "item".

But I take it from your third paragraph that you agree with the OP and myself that IDEs with good refactoring tools are a good thing.