sub rec {
  my ($hash, $parent, $seen) = @_;
  my @str;
  foreach my $k (grep { not exists $seen->{$_} } keys %{ $hash } ) {
    if ($hash->{$k}->{cat_parent_id} eq $parent) {
      push @str, $hash->{$k}->{cat_name};
      $seen->{$k} = 1;
      push @str, rec($hash, $k, $seen);
      last;
    }
  }
  return @str;
}