package Set;
use Moo;

has 'items' => (is => 'ro', default => sub { [  ] });

no Moo;

sub has {
    my ($self, $e) = @_;
    scalar grep { $_ == $e } @{ $self->items };
}

sub add {
    my ($self, $e) = @_;

    if ( ! $self->has($e) ) {
        push @{ $self->items }, $e;
    }
}

1;