WRT your last point, these features are useful when one wants to avoid repeated dereferences of list items inside loops. Doing so can give a small speed gain but my experience is that they need to avoid a pretty high number of derefs to make a meaningful difference. The same applies to Data::Alias for earlier perl versions.

A highly contrived (and incomplete) example is below. The main point is that it avoids dereferencing calls such as $path->[$i].

\my @path = $some_array_ref;

my $accumulator;
for my $i (0..@$path) {
  $accumulator += $path[$i];
}
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