Etk_Widget *etk_button_new();
Etk_Widget *etk_button_new_with_label(const char *label);
Etk_Widget *etk_button_new_from_stock(Etk_Stock_Id stock_id); // Etk_Stock_Id is an enum

##</code><code>##

sub new {
    my $class = shift;
    my $self = $class->SUPER::new();
    if(@_ == 1) { 
        my $thing = shift;
        $self->{WIDGET} = $thing =~ /\D/ ?
            Etk::etk_button_new_with_label($thing) : 
            Etk::etk_button_new_from_stock($thing);
    } else {
        $self->{WIDGET} = Etk::etk_button_new();
    }
    bless($self, $class);
    return $self;
}

##</code><code>##


$tree->Sort( \&sort_func, $asc, $column);

# the same routine but without a coderef works differently

$tree->Sort(NUMERIC, $asc, $column);

# where NUMERIC is a constant, and thus the sorting is done in C to make it faster and avoid the roundtrip to
 perl.