Hi y'all! A friend has forgotten his password, already several years back before mnemonic backups, and the bitcoins are now worth quite something. He has some idea of what it might be, but it's millions of possible combinations, impossible for him to try sequentially, but trivial for a computer to process if the right regex pattern could be supplied given some knowledge of parts of the password.

Is there such a brute force program that could be used to try a regex against a wallet.dat file?