Whenever I use Regular Expressions, my memory is always a little foggy. I usually make a couple of newbie syntax mistakes which waste some time. Now in Java (or in today's case: Ant), I don't want to edit, save (and/or compile), then run every time I alter my regular expression when first building it only to find out 10 (or more) seconds later that it doesn't match what I want or doesn't even compile.
The feedback cycle is simply too long.
After 5-10 minutes of frustration I usually seek out an online regular expression tester to ease my pain. Today I found Regex Tester and it rocks.
With instant as-I-typed feedback on my regular expressions (valid, what matches were produced for the sample string, etc) I completed the regular expressions I needed very quickly.
From now on, this site will be my first step in creating regular expressions.