Google authenticator - irule fails to lookup in data group

I am using the iRule at the end to verify the GA code. The username and the onetime code are collected in a login page that also collects the password for the AD server (username is common). It works fine as long as there are usernames only. But if I try to add a username using domain (MYDOMAIN\user) the lookup in the datagroup returns empty.I turned on logging and I do see the correct username so that is ok. Any ideas anyone? The iRule originates from here.

Thanks Carol