Attack Suggestion for Complex Passwords

[msf004]

If I have two wordlists that I want to use for a combinator based attack, but I also want to apply rules to one of the wordlists (let us say a leet ruleset). What is the best method to apply the rules of a rule-file to a wordlist; thus, creating a new and longer wordlist?

More to the point, similar the the hashcat-utils, what is the way of applying rules to a wordlist prior to actually running hashcat.