the $path (in my script's foreach) will be a reference (?)

Not a reference in the normal Perl sense (i.e. you don't need to dereference it), but an alias to the original element (which at a lower level could be thought of as kind of a reference). In other words, modifying $path will modify the original value in the array. This applies in both cases, however (with and without optimisation), because the aliases are being set up to the individual elements, even when the intermediate list on the stack is being created.