Importing encrypted passwords

[dave conz]

I need to import a database of usernames and passwords into a new vB installation. The passwords are encrypted using perl like so:
$encryptedpassword = crypt($password,"aa");

I would like to hack vB to recognize either the standard vB password or the imported (encrypted) passwords. I'm thinking that users with the old style password will be able to update their passwords as normal, and the old password will be replaced by a vB-format one.

Will this work? If so, could someone give me some pointers on where to start? Thanks.