Wikipedia
Bitflu
Bitflu is an Open Source, BitTorrent client by Adrian Ulrich. It is available for Unix-like systems and is written in Perl.
According to its official page, "Bitflu is a free BitTorrent client. The client was written in Perl and is designed to run as a daemon (7x24h , like mlnet) on Linux, *BSD and maybe even OSX"