I've just uploaded the latest devel release of File::HomeDir to CPAN. It should appear shortly.
This release contains some more POD, and a better mechanism for dieing when a method is not implemented on a particular platform.
As a result, I've now also added the documentation for, and will support, my_desktop and my_music as of the next production release.
That said, this first release is aimed primarily at testing them on Windows and Mac. There is currently no implementation of either on Unix due to the difficulty in implementing it reliably.
If anyone is an expert on Unix desktops and can provide an implementation for at least the main portion of the Unix desktops, it would be appreciated.