polymorphism

Another Kind of Polymorphism

Conway's discussion of polymorphism is couched in terms of publicly callable methods.
But a publicly callable method in a parent class might internally call a subroutine which is located in the invoking child class -- and is defined differently in each such child class.

Remember this code from Mall::Instructor?

    defined $data{$_}
      ? $self->_profile_subengine(\%data, $_)
      : print "$_ not found.\n\n";

... and in another spot ...

    open OUT, ">$output" or die;
    $self->_profile_subengine(\%data, $_);
    close OUT or die;