> Can anyone recommend a good book on regular expressions. I don't need a
> beginners book - I know how to work with regular expressions but I want
> to be able to understand and use everything and anything that can be
> done with regular expressions -I guess I would say that I need an
> advanced book.

Check out O'reilly "Mastering Regular Expressions" [1] By Jeffrey E. F. Friedl.

1. http://www.oreilly.com/catalog/regex/