I do all my Perl coding in emacs, I am not sure what an IDE would have that emacs doesnt. Or that vi doesn't.
indenting, syntax highlighting, and cvs interfacing, what else is there? Oh, debugging? Hmmm... use strict; makes it so most bugs are either obvious, or mean you need to read some man pages.
But what I'd like to see, and I'd love to work on if somebody starts, is an editing environment like emacs, but that uses perl, not lisp.