No. I would have null objects inherit from something like this (though I might not want the singleton). Because it automatically generates methods, you don't want those created for a real object. However, for a null object, it might be appropriate. For example, let's say that you have a customer and you want to get the sum total of all of his or her orders. Internally, the Customer class might have a method like this:

  sub total_all_orders {
    my $self  = shift;
    my $total = 0;
    $total   += $order->total foreach $self->orders;
    return $total;
  }
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In this case, what if some of those orders are null objects (perhaps this is a design decision that was implemented for cancelled orders), then you could have your Null::Order object:

package Null::Order;
use base 'Null::Object';

sub total { 0 }

1;
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In this case, the null order knows that its total value is zero (this example doesn't make as much sense for Perl because the false value will be converted to zero, but it's perfect for other languages).

Or you could have a null customer object get returned that has generic information for customers not in your mailing list database and automatically ignores the $customer->add_purchase; method rather than adding it to the database.