[Exim] Help with regular expressions

Hi All,

I desperately need some help with a regular expression/lookup in Exim 3.34.

I have a text file called /etc/sysconfig/exim/local_domains which contains
entries such as :

mydomain1.com
mydomain2.co.uk

I'm trying to write a 'condition' statement that evaluates whether or not a
certain Director runs based on the senders email address.

ie. If the sender is in one of the domains listed by the local_domains file,
process the director, otherwise don't bother.

My condition is :

condition = {$sender_address = /^.*@(.*)/} ${if eq {}
{${lookup{$1}lsearch{/etc/sysconfig/exim/local_domains}{$value}{no}}}{yes}}

This doesn't work :-( My problem is that the sender_address contains both a
local_part and a domain, and I just can't seem to strip the local_part before
comparing against my text file of local_domains.

Please please help,

Thanks in advance,

Paul