Okay, do you want it to return data from a database, straight text from the file, or what? At first I thought you were trying to install language modules, as did others I think. Easy enough, check the data, and return something based on that. Then I read back through and it looks like you may be wanting to return a portion of a text file, based on the query string?
Show us everything you have so far. I think this should be as easy as using a switch, but I'm not clear on what's going on so far.