as far as I understand your idea, that would require one module per filesystem. wc -l /prof/filesystems on a random Debian box shows 33 filesystems, including FUSE

Not quite; my idea is that this is all represented by "Unix Native Filesystem" because they all share the same API for querying the files. So, in its default state, VFS would just pass through to "Unix Native Filesystem" or "Windows Native Filesystem" and essentially provide nothing but unicode handling for them.

The multiple-filesystem aspect comes into play when you want to do something like browse a zip file: open(my $f, "<", "~/example.zip/path/to/Foo.txt") Currently, your only option for that is a FUSE module like fuse-zip The downside is you need to install a set-uid program for that, and the mounts of zip files are visible system-wide to all users, modulo permissions. I would much rather have the zipfile "mounted" exclusively inside the perl interpreter.

For Linux and other Unix systems, some more thinking is needed. You basically need to know if the filenames are just bytes or if they are encoded in UTF-8. Perhaps just guessing and trying to convert may work good enough for Unix

I thought I summed this up about how Unix uses 'locale', but I might be wrong! I can't find any reference to an official standard for respecting LC_ALL in path names. I've decided to make a "Meditation" about it. Coming up soon...

Edit: Meditation complete! (wow that used up most of my evening...)