use strict;
use warnings;

my @list = sort {$a <=> $b} (1, 2, 3, 6, 9, 10, 13, 22, 20, 19, 15, 21);
printf "%s\n", join(",", @list);

my @newList;
my ($min, $max);
my $count = 0;
foreach(@list) {
  if(! defined($min)) { $min = $_; $max = $_; }
  elsif($_ == ($max + 1) && $count != $#list) { $max++ }
  else {
    if($min == $max) { push @newList, ($min, $_) }
    else { push @newList, ("$min-$max", $_) }
    $min = undef;
    $max = undef;
  }
  $count++;
}

printf "%s\n", join(",", @newList);