What MySQL basically does is assign each set value a number, then uses those numbers to set and clear bits in an integer. For example:

use constant GENRE_ROCK => 0;
use constant GENRE_POP => 1;
use constant GENRE_JAZZ => 2;
use constant GENRE_METAL => 3;
use constant GENRE_LAST => 3;

sub pack_set
{
  my $bits == 0;
  foreach my $genre (@_)
  {
      $bits |= (1<<$genre);
  }
  $bits;
}

sub unpack_set
{
  my($bits)=@_;
  my @ret = ();
  my $i = 0;
  while ($bits)
  {
    if ($bits & 1)
    {
       push(@ret,$i);
    }
    $i++;
    $bits >>= 1;
  }
  @ret;
}

my $ella = pack_set(GENRE_POP, GENRE_JAZZ);
warn "Packed set is $ella\n";
print "Ella's Genres: ";
foreach my $genre (unpack_set($ella))
{
  $genre == GENRE_ROCK and print "rock ";
  $genre == GENRE_POP and print "pop ";
  $genre == GENRE_JAZZ and print "jazz ";
  $genre == GENRE_METAL and print "metal ";
}
print "\n";
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Storing the numbers in a hash instead of with constants would make it easier to print them.