Hi,
Secure proxy server deploys default examples, not sure if you have gone through the sample out of box files or not.
Should be under ~/secure-proxy/proxy-engine/examples/proxyrules
Documentation further explain them in details.
Proxy Rules Configuration - CA Single Sign-On - 12.52 SP1 - CA Technologies Documentation
I would suggest not doing anything fancy, for most of customers, proxy by host or by uri should be sufficient.
If you have multiple virtual hosts, then the hosts must be already defined by your httpd.conf as well as server.conf.
I do think there needs to be a default proxy rule section, where everything is caught if logic is somehow flawed in configuration.
Thank You,
Hongxu