That works, but here's an alternative that may run faster.

The code on that page isn't quite what you want, but it's close: It checks all possible strings of 8 characters. You would probably want to fix up the code to only do the letters. If you did that, you would be able to get rid of the map. Of course you'd want to change the success condition also.

I'm really glad we got to discuss this, because up until now I thought the code on that page was completely useless, and now I know it's only almost completely useless.