my $appearances = [];
while ( my $ref = $sth->fetchrow_hashref() ) {
   my $season = $ref->{season};
   unless ( exists $appearances->[$season -1 ] ) {
      $appearances->[$season -1 ] = { season => $season, eps => [] };
   }
   my $eps = $appearances->[$season -1 ]->{eps};
   push @$eps, $ref;
}

##</code><code>##

$appearances = 
[
    {season => 1, eps => 
      [ 
        {season => 1, ep => 1, title => 'Hellmouth' },
        ......