forward to other domain

Can anyone tell me how to make procmail to fetch a username in the to 
field (like in username(_at_)domain1(_dot_)com) and forward the email to 
another domain but with the same username, such as 
username(_at_)domain2(_dot_)com?

I have come this far with my recipe:

# grab $USERNAME somehow..... ???

:0
*   ! ^FROM_DAEMON
! $USERNAME(_at_)domain2(_dot_)com


Thanks in advance,

Tomas Karlsson
webmaster(_at_)iimagers(_dot_)com