CORS iRule Problem

SiteA and siteB are behind the same VIP, I just use an iRule to determine which pool gets hit based on the URL and they both get authenticated by APM.

I wrote this based on my understanding of CORS, but when I look at the traffic in fiddler, I never see a CORS header. Anyone who's done this know where I might be going wrong or if I'm completely misunderstanding how CORS is supposed to work?

I've read a few other posts on here related to CORS, but the solutions didn't seem to work for me.

Any help is appreciated!