Your logic above is broken; if any attempt succeeds, you undo it by trying another method. If you don't care about trying a lot of possibly broken path alternatives, you could do this:

open(MENU,  $bestpath  ) or
open(MENU,  $nextbest  ) or
open(MENU,  $worseway  ) or
open(MENU,  $fallback  ) or die "No way to reach it!";

do_stuff_with MENU;

close(MENU) or die "Scary failure trying to close it!";
[download]

If you're just asking what the right syntax would be for a UNC path, it's \\netbioshost\sharename\path\to\file.ext.