I'll try to stick to the more unusual things, since most of what I do with Perl is pretty vanilla.
Processing camera input
Generating graphical OpenGL output (OpenGL::Simple, attempting to use OpenGL, a few others)
Processing SDL events (keyboard, mouse)
Sending and receiving automated Jabber messages (Net::Chat::Daemon) to monitor autobuild system, wiki edits, manual builds, etc.
Interfacing between C++, JavaScript, and Flash code
Monitoring revision control systems and running checks, sending out commit messages, figuring out who to blame for the commit(s) that broke the automated build, etc.
Implementing Perl-style "regular" expressions with backends in Perl5, Parrot, and C.