[exim] Capture matched value of match_ip

Hi,

I am trying to capture the value that matches the given IP address in
match_ip operator, for instance,

set acl_m1QQ = ${match_ip{$sender_host_address}{${sg {${lookup
mysql{TAG_BADNETWRKS}}}{\n}{:}}}{$0}{0}}

The result is "0" when it should be something like "12.3.123.0/24".

I've tried $value instead of $0.
I've tried set acl_m1QQ = ${if match_ip ... Also. No luck. I've read the
documentation for match_ip and there's no mention of capturing the
value.

Thanks.
Craig