[exim] greylisting + white list recipient

I've been asked to implement greylisting with exim but I must maintain
the ability to white list by recipient addresses. I'm using:

   defer message = Greylisted - please try again a little later.
         !hosts = +exclude_greyhosts
         condition = ${if eq{$acl_m2}{0}{1}}
         condition = ${lookup mysql{GREYLIST_ADD}{yes}{no}}
   defer message = Greylisted - please try again shortly.
         condition = ${if eq{$acl_m2}{1}{1}}

in my acl_check_rcpt. So I added:

!recipients = ${lookup{$local_part}lsearch{/etc/exim/exclude_greyrecip}}

because I just want to have a list of local parts in a file. If I sent
an email to an address listed in the exclude_greyrecip list it still
gets greylisted.

I've tried a few combinations and the only thing so far that has worked
is putting the full email address in exclude_greyrecip and just putting:

!recipients = /etc/exim/exclude_greyrecip

Any ideas on how to match only the local parts?

Thanks in advance,
Gary