GD::Graph::Pie -> http://search.cpan.org/tools/GDGraph
-> http://search.cpan.org/grep?cpanid=RUZ&release=GDGraph-1.48&string=percent&i=1&n=1&C=0
-> http://search.cpan.org/grep?cpanid=RUZ&release=GDGraph-1.48&string=%3A%3Apie&i=1&n=1&C=0

samples/sample91.pl
samples/sample92.pl
samples/sample93.pl
samples/sample94.pl
[download]

I would look at samples 91 through 94, look for "legend" or "label"