In order to keep it as simple as possible, we can avoid the need to define some objects as variables. For example, connected networks, so we can apply rules with the following syntax.

pass inet proto tcp from vtnet0:network to any

Which saves us the equivalent.

red=vtnet0:network
pass inet proto tcp from $red to any

Or its equivalent.

red=192.168.1.0/24
pass inet proto tcp from $red to any