Perhaps you could Tie it to a filehandle and use flock? I'm going to stick my neck out and guess delete is atomic and thread safe. Just as a philosophy pointer - design something to break your program, there's nothing like empirical destructive stress testing to get the answer. Write a couple of very impolite thread loops to compete over a hash and set it running for a few hundred thousand cycles, see if any collisions occur.
BOL.
Andy.

Update: I found this for you.
hash util