mysql proxy startup command:

mysql-proxy --admin-username=a --admin-password=b  --admin-lua-script=/usr/share/mysql-proxy/admin.lua --proxy-backend-addresses=127.0.0.1:3306 --proxy-lua-script=/home/sven/myscript.lua


Introduction:
http://www.oreillynet.com/pub/a/databases/2007/07/12/getting-started-with-mysql-proxy.html