pdl> p $x = floor random(5) * 10
[9 4 3 2 8]
pdl> p Dumper($xperl = $x->unpdl)
$VAR1 = ['9','4','3','2','8'];
pdl> $xperl->[ $_ -1 ] -= $xperl->[ $_ ] for reverse 1 .. $#$xperl;
pdl> p Dumper($xperl)
$VAR1 = [14,-5,9,-6,8];