Different homepages based on cookies?

Hey guys,

I’m wondering how to serve a different homepage to a visitor depending on the existence of a cookie.

I presently have a wordpress instance that serves as a marketing site for a SAAS product. We have a link in our header for login that takes users to the sign-in page for our app, which is totally separate from wordpress.

I’d like our “keep me logged in” cookie to cause wordpress to take them to a custom page that focuses on the login process and some advocacy initiatives we have.

I tried searching, but wasn’t coming up with anything. Thanks for all the help so far, been lurking for years now, and I always find answers without having to ask questions.