A quick CPAN search turns up Digest::Perl::MD5:

NAME
    Digest::MD5::Perl - Perl implementation of Ron Rivests MD5
    Algorithm

DISCLAIMER
    This is not an interface (like `Digest::MD5') but a Perl
    implementation of MD5. It is written in perl only and because of
    this it is slow but it works without C-Code.
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Hope this helps :-)

-- 
Joost       downtime n. The period during which a system
            is error-free and immune from user input.
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