my $_added_columns = 0;

sub add_column {
    my $self = shift;

    if ( ! $_added_columns++ ) {
        $self->_initialize_class();
    }
}

##</code><code>##

my $_objects_created = 0;

sub new {
    my $self = shift;

    if ( ! $_objects_created++ ) {
        $self->build_class();
    }

    # construction continues
}

##</code><code>##

__PACKAGE__->initialize_class();
__PACKAGE__->add_column('name');
__PACKAGE__->add_column('address');
__PACKAGE__->build_class();