[exim] Fetch regexp for match from database

Hi,

I reject some generated recipient addresses that are spammed:

deny
message = ...
domains = +local_domains
condition = ${if match{$local_part}{[0-9]+}{yes}{no}}

But I'd like to get the regexp from a database:

condition = ${if match{$local_part}{{lookup pgsql{SELECT
'[0-9]+'}}}{yes}{no}}

But I get an error:
invalid "condition" value "}{yes}{no}}"

Isn't that possible this way? Is there another solution?

Thanks a lot,

Thomas