use strict;
use warnings;

my @list = sort {$a <=> $b} (1, 2, 3, 5, 9, 10, 13, 22, 20, 19, 15, 21, 33);
printf "%s\n", join(",", @list);

my @newList;
my $min = my $max = shift @list;
for(@list, -1) {
  if($_ == ($max + 1)) { $max++ }
  else {
    if($min == $max) { push @newList, $min }
    else { push @newList, "$min-$max" }
    $min = $max = $_;
  }
}

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