DB<62> sub tst { print "$_: ", ($_ <=> $l) + ($_ <=> $r), "\n" }

  DB<63> ($l,$r)=(1,4)
 => (1, 4)

  DB<64> tst() for 0..6
0: -2
1: -1
2: 0
3: 0
4: 1
5: 2
6: 2