Obfuscate usernames that have email address info in them.

[minorgod]

I'm looking for a mod that will tweak the username display of any user that has used their email address as their username, so that it will only display the part before the "@" symbol. I'd rather do this as a plugin than a template modification. If someone can tell me which hook to use and the name of the template variable that will need a preg_replace() done on it, I can make the plugin myself, but I'm new to vBulletin (just switched from phpBB) and I'm not sure where the code should go. Oh, and I'm using vBulletin 3.6.