[exim] alternative to local_part_suffix in ACL?

Greetings.

I'm trying to figure out a way to do LDAP lookups using a portion of
$local_part in an ACL, similar to using $local_part_prefix in a router. This
following lookup works just fine for normal exact matches:

  accept
    condition = ${lookup ldap {ldap://localhost/dc=example,dc=com??sub?\
                 (|(mailLocalAddress=$local_part@$domain))} {yes}{no}}

What I would like to do is something similar to this:

  accept
    local_parts_suffix = -*
    condition = ${lookup ldap {ldap://localhost/dc=example,dc=com??sub?\
                 (|(mailLocalAddress=$local_part_prefix@$domain))} {yes}{no}}

This isn't possible currently because local_parts_suffix is not a possible
option during an ACL. I would like to have some method of extracting part of
the value in $local_part to allow for an LDAP lookup on a selected portion of
the value.

I'm looking for hints as to how I might go about doing this. [Perhaps
something can be done with ACL variables and regexes?]

    - Chris

--

Chris Knadle
Chris.Knadle@???