The best “you can’t parse Aitch Tea Em Ell with regex, have you considered using a parser?” screed ever written: http://stackoverflow.com/questions/1732348/regex-match-open-tags-except-xhtml-self-contained-tags/1732454#1732454 […] HTML tags lea͠ki̧n͘g fr̶ǫm ̡yo͟ur eye͢s̸ ̛l̕ik͏e liquid pain […] is just effing brilliant.
This actually sounds like fun: Regex golf [1]. From xkcd, natch. [1] http://xkcd.com/1313/
Something like this is better suited to being handwritten on vellum with illumination and gilt edged pages and bound in a leather tome. Barring that, this page is all you need to craft a regular expression to match (or not match) any thing or set of things in the universe. Behold the Regular Expressions Cheat…