[exim] Stupid lsearch/lookup-question?

I am trying to figure out how to make a simple lookup work right.
Basically, I have a file in the form of

Username:    yes
Username2:    yes

And I want to trigger a router if the user is listed herein. My current
lookup does not seem to trigger as expected

domain_redirect:
        driver = manualroute
        domains = mydomain.com
        local_parts =
${lookup{$local_part}lsearch{/etc/exim4/domain-redirect}}
        transport = remote_smtp
        route_list = * 192.168.0.201
        host_find_failed = defer
        same_domain_copy_routing = yes
        no_more