I want to point out that regex may not be the right base to start from. The key thing that I am seeing is ALL of your sample strings to look for have been simple strings, with NO "regular expressions" in them (things like optional strings, alternates, or repeats). When you include those options theanswer you are looking for become not practically computable as there may be many possible "difference sets" to make the match. Also, how close do you need? Can I say that I find fun in foobar with a mismatch on the second and third characters? (if so you will hit a LOT of partial matchs). As has been pointed out, you need a precise definition of the mismatches allowed and then you can work for that. I personally do NOT think regex is apt to give you the results you want, because I get the feeling that you are going to want to know how close the match is, and regex only really know if it matched or not. Richard Damon.