That would be a great suggestion, except we that we seem to be constrained to integer coordinates.

I can't think of any way to avoid dealing with the four sides of the square separately. You might try replacing the range loop body with something like the fragment below. I think it's somewhat easier to understand, and it doesn't print each corner of the square twice (though it does miss the origin).

  my ($x, $y) = ($range, $range);
  while ($x > -$range) { print "$x,$y\n"; $x-- }
  while ($y > -$range) { print "$x,$y\n"; $y-- }
  while ($x < $range)  { print "$x,$y\n"; $x++ }
  while ($y < $range)  { print "$x,$y\n"; $y++ }
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This shows why it's nice that perl lets you do what you want with whitespace, unlike some other languages.