method _create_pattern_obj (Str :$name, Maybe[Str] :$mask_data, Maybe[Str] :$tag_data) {

    my $tags = {};
    map {$tags->{$_} = 1;} split(',', $tag_data) if defined $tag_data;

    my $pattern_obj = Program::Plist::Pl::Pattern->new(name => $name,
                                                       mask_data => $mask_data,
                                                       tags => $tags);

    $self->_add_pattern($pattern_obj);
  }