DB<120> @order=1..5
 => (1, 2, 3, 4, 5)

  DB<121> $last= $order[0]
 => 1

  DB<122> for $cur (@order[1..$#order]) {
           print "$last,$cur\t";
           $last =$cur;
           }
 => ""
1,2	2,3	3,4	4,5