You could perhaps use a second dimension to keep track where the element came from...

@array = (3,2,1);
$array[4] = 0;
my $i = 0;
foreach (
          sort { $a->[1] cmp $b->[1] } # or better <=> for numbers ins
+tead of cmp
          map { [$i++, $_ ] } @array
         ){
  my $number = $_->[1];
  my $originalIndex = $_->[0];

  # do something with $number and $originalIndex...
} # foreach
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Best regards,
perl -e "print a|r,p|d=>b|p=>chr 3**2 .7=>t and t"