Algorithm::KMeans is a perl5 module for the clustering of numerical data
in multidimensional spaces. Since the module is entirely in Perl (in the
sense that it is not a Perl wrapper around a C library that actually does
the clustering), the code in the module can easily be modified to experiment
with several aspects of automatic clustering. For example, one can change
the criterion used to measure the "distance" between two data points, the
stopping condition for accepting final clusters, the criterion used for
measuring the quality of the clustering achieved, etc.

WWW: http://search.cpan.org/dist/Algorithm-KMeans/