Tokens not working with "fills out form" trigger in referrer constraint

Hi there!

I am trying to use a token to set a referrer constraint in a "fills out form" trigger, but the trigger will not fire with the token. I have verified that:

1. The trigger works fine when the full URL is entered into the referrer
2. The trigger does not work when I use a token instead with the following combinations:
   1. Referrer Contains: Token
   2. Referrer Is: Token
   3. Referrer Contains/Is: {token without }
   4. Referrer Contains/Is: {token without }
3. There are no red squiggly lines when I use the token, so Marketo is accepting it.

Any ideas? Thanks in advance!

Eric