It works fine and makes switching machines really simple, at least for me. The drive perl has to be on is which ever drive apache's CWD is on. So if apache's cwd is "C:/foo/bar/", "/usr/bin" will refer to "C:/usr/bin". But if apache starts under D: or some such, it needs to be there. Also note, last I checked, you don't need the entire perl install in this new directory, you can simply add a shortcut named perl, and that should work.