Toadstool is a library for pattern matching. The author is Stanisław Halik, and it is released to the public domain.
Toadstool has been criticized for having an unlispy syntax, but that concern appears to have been rectified.
The Git repository is at http://tehran.lain.pl/git/toadstool (browse it).
A mirror at github is at https://github.com/kisp/toadstool.