[Exim] Can this be done with Exim?

Okay. Somebody please excuse this newbie Exim administrator question, and
if this is answered somewhere in the documentation, I can't find
it... directing me to a good place in the FM to read is welcome. Part of
the problem is I don't know exactly how what I want to do is described.

In sendmail, it is possible to have a aliases file like this:

user1@??? user@???
user2@??? user@???
user1@??? user@???
...

In this fashion, user1@??? can point to a different alias than
user1@???. (I understand the mechanism in sendmail is a bit
different than this, I'm just trying to demonstrate what it is I want to
do). It's kindof an advanced virtual domain kinda thing.

Plese help me out on this. Thanks.

-Chris S.