NFAs and DFAs
jlouis: http://swtch.com/~rsc/regexp/regexp1.html is a must read.Then you should probably listen to http://www.cs.brown.edu/~sk/Publications/Talks/SwineBeforePe... by Shriram Krishnamurthi (I've met him - He is a really cool guy). At that point you have the ammunition and the gun loaded. You just have to fire it.