Thanks everyone.

Those approaches will be very useful. I could have made it clearer I guess, that I can program my way to a solution, but was wondering if regex would have it built-in, so I could just use  "cat dictionary-file | grep /Z1[AABCDEF]/Z2where Z1 or Z2 is a magic modifer that forces each letter in the  [ ]set to be used only once. It looks like not. But you never know, there's a world of functionality in regexp and anything that feels like it could be in there, or would have been asked before, usually is in there.

Well back to WordsWithFriends on iPhone ! The dictionary for that game has 173000 words and a vast number I have never heard of, not to mention English/US/other spellings etc. My friends just experiment with words until they find something it accepts and I need to fight back ! Not really fair but I need a few wins.