Those are in fact the two modules for which I am now working on new versions. (Both original authors have agreed to make me co-maintainer.)

Your comment sounds like you're recommending my choice 2 (copy the scheme of the target URL). That's what ProxyPAC does now. ProxyAutoConfig simply returns what FindProxyForURL returns, namely a URL without a scheme.

I'm trying to resolve an HTTP::ProxyPAC bug report against returning the target scheme, in which the reporter states that one can't have more than one scheme/protocol on a given port. That's true for an endpoint server, but I'm not sure it's true for a proxy.

But consider what the next-downstream software entity (like LWP::UserAgent) needs to do. It needs to send its request/original URL to the given port on the proxy, which is identified by either its name or its IP address. One purpose of a scheme is to identify a default port (like http->80), but we already have an explicit port. The other purpose of a scheme is to identify the protocol that should be spoken/exchanged.

I think I will try and see how LWP::UserAgent reacts if I give it a proxy without a scheme, and let its response dictate whether or not to go with choice 3. Then I will interact with the proxy at work to further refine the proper choice. Unless anyone else has further words of wisdom.

Thanks for replying,
cmac