[exim] Execute shell command on condition

Hello,

This is what I have so far and it works perfectly fine the way I want it to:

drop message = No such user at domain.com
        condition = ${lookup mysql{select username from usernames
where username='$local_part'}{no}fail}

However, I would like to do one additional thing; whenever the above
condition returns true (that is the message is being rejected) I would
like to execute the shell command "perl denyexim.pl
$sender_host_address".

Please let me know how to do this!

I do have embedded perl enabled however I just need to execute that
shell command, I dont need to test any further conditions. If I
understand correctly embedded perl is used when you need to test
further conditions or parse a result into perl for further processing.

Thanks & Regards,
Fahd