if (substr($record,  0, 10) =~ $src_ip_of_interest
and substr($record, 10, 10) =~ $dst_ip_of_interest
and substr($record, 20,  4) =~ $proto_of_interest
and substr($record, 24,  6) !~ $src_port_of_disinterest
# etc ...
) {
    #we found a record that matches the query
}