My favorite editor right now, is vim; however, that's not really an IDE. There is a windows version, but I prefer Komodo Edit on Windows.
Komodo Edit says that it's a text editor, but it does quite a bit more. It can be linked to the perl interpreter and can emulate vim commands, so it's very powerful. There is also the Komodo IDE, but I haven't used it, and it isn't free, so I can't comment on it.
A lot of people like Eclipse with the EPIC plugin. (EPIC has the Perl extensions for Eclipse.) It can also be linked to Perl, and has a lot of nice features. It's written in Java, so it can eat a bunch of resources sometimes, but it can run on lots of platforms.