sub     get_sorted_intervals_as_array {
        my $atree = shift;
        my @ret = ();
        $atree->traverse(
                # specify a func to be run on every node as returned b
+y traverse()
                sub {
                        my $anode = $_[0];
                        print "traverse() : ".$anode->{interval}." => 
+".$anode->str()."\n";
                        push(@ret, $anode);
                }
        );
        return @ret
}