Doesn't look like it as such, but peeking under the hood what you could do is to create an RPC::XML::Server instance with no_http set to true, then have your own HTTP::Daemon code which passes the body of any XML-RPC calls off to the dispatch() method. Anything which needs to return an XML file would return a URL which your HTTP::Daemon handle itself (rather than passing off to the RPC::XML::Server).

Hopefully that made some sort of sense. :) Read the docs for RPC::XML::Server, specifically the arguments for new() and the description of dispatch().