RegExPlus - Java regex library (now free)
RegExPlus extends Java's regular expression syntax by adding support for additional Perl and .NET syntax.
These additions make it possible to use the same regular expression in Java that you already use in other RegEx engines.
100% backwards compatible with Java regular expressions plus the below additional syntax.
Also available: JavaStar - online regular expression tester that uses RegExPlus to check for matches.
Sorry for the long wait, RegExPlus is finally free to download for both personal and commercial use.
For the record, don't fall prey to peer pressure. When friends tell you to sell something that you want to give away for free, don't listen to your friends. Again, sorry for the long wait, enjoy the library.
Check out the forums to Ask for Help, file a Bug Report, make Feature Requests, or to check out and share Tips and Tricks.