Using realms without proxying

Hi everyone, I'm using freeradius-2.1.4 with MySQL and would like to set up realms without proxying. The reason is that I'd like to keep all the requests to a single Radius server, however would like to separate the users' radreplies based on their username/groups. I know that I can use groupnames to have group based policies but I would like to have the groupname as part of the login name, hence the realms. The main reason for wanting to set up realms is so that I can have a username with username@groupname format and use the variables %{Realm} and %{Stripped-User-Name}. When I do set up realms, it seems that I have to proxy. Is there another way of accomplishing this? James