Joke filter program, written by JohnPC, to turn ASCII text upside-down, using output in unicode where necessary.
You can either download the latest version, or take a peek at the source.
Now also available as an irssi plugin, thanks to EricV.
New! Now there's also a proper module that implements this, Acme::Rot180, version 0.20.. but this release is currently not on CPAN yet: I need to clean up the documentation a bit and add the "uniud" script itself. But at least the module is here for you to look at. Now also includes a turned uppercase K :)