It is quite different. An explorer namespace extension is different from FUSE. It might use similar parts of the code, especially the parts talking to Google. The mechanisms of talking to the operating system are completely different. All of this is no matter of Perl though - both are talking to the operating system at a far lower level.

If you want something like this in a cross-platform way, you will need to write or to find a module that exposes the same API to both FUSE and an Explorer Namespace Extension - which is not easy, and surely not conveniently done in Perl.