Since you mentioned: code folding, the built-in regexp tester and perl-tidy, the syntax colorization, the easy click into modules, the real-time syntax and warnings checks. You might look into jEdit (www.jEdit.org).

It is the only single IDE I have found so far that includes everything you specified, as well as run on both platforms. It is open source. If there is another one out there I'd enjoy to hear about it.