Unknown Error creating file '/afs/hcoop.net/user/z/za/za/zacha/wordpress/wp-content/plugins/ttftitles/cache/06123ae2ad649f1b69fcb99bf48983e0.png'.Anyone know of a good regular expressions tutorial?

I want to futz with my Pipes, but last time I tried I couldn’t find anything terribly user friendly, and ended up resorting to guess-and-check.