A Perl script which analyzes the OS it's running on top of to determine whether or not it's virtualized, and if so which product(s) it's inside of. Uses multiple techniques (no red pills, I don't think) to gather information.
A Perl script that logs into a MySQL database server (with or without credentials), analyzes it, and makes suggestions to optimize its performance.
FOSS software which implements a mailing list, not just over email but as a sharable, clonable git repo. Implements nntp, online html archives, and atom feeds. Written in perl. Designed to run on the lower possible common denominator machine. Uses a pull model, which optimizes for casual readers and members while still allowing for serious users.
Kareha doesn't use a database, Wakaba does.
Just what it says on the tin. Implements Z-code with cheat commands so you can play Infocom games on whatever system you have Perl installed on. Supports multiple front-end interfaces.