for people who are coming to this topic, here is another regex helper app -- web based and free, though you'll have to translate from perl regex to python regex once you're done; mostly just some syntax stuff, for instance - perl has no (?P<tag>) captures, just '()'. i use this site often to help me when i'm stuck on a particular regex problem.
http://www.gskinner.com/RegExr/
it's flash-based, but very worthwhile. the tooltip debug info and highlighting really make it worthwhile, imo.