I think a 'good' IDE is one that bundles all your other tools (editer, debugger, etc.) in such a way that you're able to work in a single, common environment. For perl I use Eclipse with the EPIC plugin. It supports the debugger, perltidy, revision control (with another plugin for svn, for example), perldoc, code folding, etc. Also has an integrated 'web browser' for developing cgi scripts locally.