I have run the gauntlet of learning and applying regular expression syntax many times for many different purposes. I never seem to retain it, so I have to relearn it every time.

It is never a pleasant task, but one that always leaves me smiling just because I am always so glad when it's over. It is so incredibly powerful, it's hard not to appreciate.

I have used several different regular expression parsers, most commonly the one in the standard java library, lately.