If you prefer the hard way, here is the official RFC describing the MD5 Message-Digest Algorithm. But be careful, MD5 is a one way hash algorithm, you can't decrypt it! or we would have the best compression method of the world :) Good luck...

Ciao, Valerio

Update: Digest::MD5 is now shipped with perl-5.8.0; swiftone, it isn't written in Perl, it is C code...