You can use the no_proxy method of LWP::UserAgent to specify hosts or domains that should not be passed to the proxy server. It takes a list of strings that are matched verbatim (i.e. the strings are not regular expressions against the host name in the URL).

The match is anchored to the end of the host name which, if the host name is a fully qualified DNS name, allows one no_proxy string to match any hosts within that domain.

I don't see any provision for easily excluding URLs by network (e.g. 192.168.0.0/24). You could list all the IP addresses in the network.