`NEXT.pm`

Consider this class inheritance structure:
Now consider D::DESTROY
- We would like D::DESTROY to call B::DESTROY (if there is one)
- Moreover B::DESTROY should call A::DESTROY (ditto)
We can accomplish that this way:

        # Package D
        sub DESTROY {
          my $self = shift;
          # Do various destructions here
          $self->SUPER::DESTROY;
        }

SUPER::DESTROY means "call DESTROY"
- If B::DESTROY also calls SUPER::DESTROY, everything works as it should