Pattern matching in Python
monkey.org
monkey.org
Also, doing anything by overloading arithmetic operators for a semantically unrelated purpose tends to be pretty disharmonious with the rest of the language. The only exception I can think of is Lua's LPEG (http://www.inf.puc-rio.br/~roberto/lpeg/lpeg.html), but that's a specific sub-language that tends to be clearly isolated to grammars; in practice, it's usually as distinct as using * within regular expression strings.
I wrote some pattern matching code myself for python a few months back just for fun. It was extremely unpythonic, but a fun exercise. For comparison, here's my code:
http://github.com/paulgb/python-pattern-matching/tree/master
* http://codespeak.net/pypy/extradoc/paper/prolog-in-python.pdf
* http://mail.python.org/pipermail/python-list/2005-October/348485.html
I think Peter Norvig has written about this, too.