[Exim] Problem with lookup

Hallo,

in Exim 3 I have the following Section in my config file:

require_files         = "/etc/exim/${lookup \
                         {${local_part}@${domain}:file} dbm*@ \
                         {/etc/exim/autoresp.db} {$value} {_} }"

The file autoresp have the following entry:

localpart@domain: from="Realname" file="filename"

Here I will get only the filename to verify if the file exist.
In Exim3 it works, but in exim 4 not.

I become the following error:
failed to expand "/etc/exim/${lookup {${local_part}@${domain}" for require_files: missing } at end of string

Can someone help me, why ?

Thanks.

Regards,
Michael