This adds support for <nil> value, a XML-RPC extension.
http://ontosys.com/xml-rpc/extensions.php

http://rt.cpan.org/Public/Bug/Display.html?id=20569

diff -up SOAP-Lite-0.710.07/lib/XMLRPC/Lite.pm.nil-value SOAP-Lite-0.710.07/lib/XMLRPC/Lite.pm
--- SOAP-Lite-0.710.07/lib/XMLRPC/Lite.pm.nil-value	2008-06-05 20:43:44.000000000 +0200
+++ SOAP-Lite-0.710.07/lib/XMLRPC/Lite.pm	2008-09-09 15:10:21.000000000 +0200
@@ -314,6 +314,9 @@ sub decode_value {
     elsif ($name =~ /^(?:param|fault)$/) {
         return scalar(($self->decode_object($children->[0]))[1]);
     }
+    elsif ($name =~ /^(?:nil)$/) {
+        return undef;
+    }
     else {
         die "wrong element '$name'\n";
     }