while (my($slot,$value) = $filterSth->fetchrow_array()) {
  if ($filerHash{$slot}) {
     //slot already exists, just append to it
     my $existingValue = $filterHash{$slot};
     my $newValue = $existingValue . " | " . $value;
     $filterHash{$slot} = $newValue;
  } else {
     //slot does not exist, just add it
     $filterHash{$slot} = $value;
  }
}