I'm not sure this is relevant, but perhaps this solution of mine to a similar problem could give you some ideas: Re: Minimal password check, again.

Here's the sample use and output from Re: Minimal password check, again:

    check_reps('xattattttatty');

    __END__
    att repeated 2 times, covers 46%
    ttatt repeated 2 times, covers 76%
    tt repeated 2 times, covers 30%
    t repeated 3 times, covers 23%
    t repeated 2 times, covers 15%
    t repeated 2 times, covers 15%
[download]

Hope this helps,
ihb

Read argumentation in its context!