Alright so I figured it out! This is actually pretty easy. You’ll just need to use regex to find matches. As for the expression, if I am just checking for one domain I would enter:

(amazon.com)

If I wanted to check for a match among multiple domains, just add the | separator:

(amazon.com|walmart.com|costo.com)

So as you can see in this screenshot, the workflow item will only execute if (looking at the input box) the user included a domain NOT on that list. Hence why :count is 0 (no match). If I wanted to require a match, I’d simply use :count is 1.

Hope this helps someone!