Which version of ActiveState Perl are you using?

From two different systems with different versions of ActiveState Perl (version 5.8.9, version 5.12.1 x86), I was able to find and install XML::XPath version 1.13 from ActiveState's repository using the the PPM in GUI mode.

To use the PPM in GUI mode, you can type ppm in a command prompt and hit enter. When the PPM starts, it will automatically try to connect to the configured repositories to sync up its local database listing of the modules available in those repositories. (If you're behind a proxy server, you'll need to update PPM's configuration with the proxy server details so that it can connect to the repositories.) By default, the only repository configured is the ActiveState repository.