[Exim] ,forward file question

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I have an autoresponder that checks the incoming address against the database
of users to determine if the incoming mail chould get an autoresponse or not.
The .forward as it is now - just one line:
\username, "|/usr/bin/perl /home/username/www/cgi-bin/autoresponder/receive.pl"

The problem -
The srcipt sends an error email if the incoming message does not have an existing
user in the database - such as support@ , info@ or whatever else may be real addresses
that we need to have.

The question -
What is the opinion of the group as to how to filter the incoming messages and keep
the error message from being sent?
Can .forward provide this capability? How?
Would a procmail recipie be more flexible? If so - can anyone provide an example - I am
not a procmail person. :)
Thanks for any help,
John A. Buck

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