Did you check if the $client is built properly? You could add another print Dumper($client);. I just think the line my $client = RPC::XML::Client->new('http://localhost:8000/'); looks doggy, don't you need to specify the name of the service in the URL? Something like 'http://localhost:8000/cgi-bin/rpcserver'.

And you could also invoke the perl debugger and step into the send_request method, and see step by step what is happenning inside the module. Are you on Linux? If so, you could just invoke the ddd visual debugger by specifying -perl on the commandline, together with the name of your script.