This is the quick hurrah. I will later write a longer post on how to get a single tile feature from mapserver. If you have been hitting your head against the wall trying to find this out for hours, then you will get what I will say.
1. You are going to use the cgi program. I still haven't figured out how to server tiles using MapScript
2. You are going to use variable substitution, which information is documented in a koan manner on this page http://old-mapserver.gis.umn.edu/doc/mapfile-reference.html#variablesubs...
Filter "%funkyvar%"