No, this is not about search engines. A "query" targets a specific web page ...

Same difference :) a search engine is nothing bu a specific web page, and all those modules do is return ... frabular ... data from those "web pages" using the same interface

sub whatever { WhateverYourModuleDoesOrExports(%args) }

A plain ol function, no akward OOPy registering (or whatever that is supposed to be, the part that I don't understand)