Conditional based on referrer?

I have a website with an accompanying staging site for testing purposes. I want to create a CFIF that checks where the request is coming from (live.mysite.com vs. development.mysite.com), and then execute code based on the origin. For reasons I won't go into here I can't pass anything in the URL scope.

I've looked in some documentation but don't see anything that helps.

Ideas?

THANKS...!