Win32::WebBrowser starts the default web browser on Windows.
I tested it by changing around the default browser and pointing the module both at files on my system and the world-wide web, and I'm glad to say that it works exactly as stated, but it would be nice if the module was integrated slightly better into the Perl ecology.
At the moment it is set up to fail "make" and "make test" if $^0 is not set to 'MSWin32', hence the failed tests on Linux systems. Just for the sake of the CPAN testers, the make script should be set up better to detect the OS and do something more sensible than just going kaboom.
Also, despite the way it is set up, the module installed and ran perfectly on Cygwin after I'd commented out parts of the installation scripts (most of t/01load.t and lines 14-22 of Makefile.PL).