use warnings;
use strict;

my @array = (5,2,6,8,10,1,4,7,4,2,21,18,25,10);

my %list;

while (my ($i,$v) = each @array){
    $list{$i} = $v;
}

print "val: $list{$_}, idx: $_\n" 
  for sort {$list{$a} <=> $list{$b}} keys %list;

__END__
val: 1, idx: 5
val: 2, idx: 1
val: 2, idx: 9
val: 4, idx: 8
val: 4, idx: 6
val: 5, idx: 0
val: 6, idx: 2
val: 7, idx: 7
val: 8, idx: 3
val: 10, idx: 4
val: 10, idx: 13
val: 18, idx: 11
val: 21, idx: 10
val: 25, idx: 12