I've ran into Kite, and impressively complete framework for the design and construction of kites, by the author of Template Toolkit.

Also, by Paul Fenkwick, there's a module to assist in calculation of no-decompression diving times, SCUBA::Table::NoDeco.

Weewar is a Perl interface to the online turn-based strategy game Weewar.

I'm pretty sure there are many more!