You'd actually want to do this with a field extraction, but you could test the field extraction with the rex tho.
Something like this in your local/props.conf
[host::x.y.z.b]
EXTRACT-ip_proto,src_address,src_port,etc = "list 101 denied (? [a-zA-Z]+) (? d+.d+.d+.d+)((? d+)) -> (? d+.d+.d+.d+)((? d+))"
You'll need to customize the extracted field names to match.
... View more