Got it. This actually bit me in the past.
Use this:
Code:
table <direct_servers> const { 172.26.0.24, 172.26.0.32, 172.26.0.39, 172.26.0.41 }
rdr on $int_if inet proto tcp from $int_if:network to ! <direct_servers> port www -> 127.0.0.1 port 3128
I think something prevents negating 'multi-value variables' (or maybe even single-value ones), whereas tables are not a problem.