This looks a little more natural:

my @a = (1 .. 9);  # for instance!!
   for my $e (@a) {
     my $ee = $e+1;  # copy current element
   }
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In any case it's a trade-off. The current way allows you to modify the array in-place while still allowing you to easily, I like split infinitives BTW, use the elements without changing the array. If $e was just a copy it would be much harder to modify the array in-place. That's a good deal I think.