Markdown what does it take to parse you

Its been 4 designs trashed since I've got this need to write a Markdown to HTML convertor in Factor. The catch: I don't want to use regular expressions. I'm trying to make it really generic but some stupid edge case comes along and crashes the parser. Talk about morale sapping. Particularly when I'm already quite frustrated. This is the only frustration which I can rant about in public.