I am also curious about this. My model is for example: "use Tk;". That "uses" Tk::Ballon, Tk::Frame and a bunch of stuff via autoloader.

Go look at your Perl directory and look at the sub-dirs.

Try this: C:\ls perl ..which on my system prints...

bin    cpan    eg    etc    html    lib    man    site
[download]

If MassSpec is a correctly installed module, then it will work.