I wonder what techniques people use for debugging regexes.

Some tools I thought would be useful

1. proofreader to help get \ quoting right.
http://mindprod.com/project/regexproofreader.html

2. composer http://mindprod.com/project/regexcomposer.html

3. some sort of tool when you don't get a match to give you the index
of the rightmost char that DID match.

4. a framework when you give your patterns and test strings and it
tells you which match and which don't.  Perhaps it could prune
strings/patterns to find the best match.