eval.c:1201
static VALUE
eval_node(self, node)
    VALUE self;
    NODE *node;
{
    NODE *beg_tree = ruby_eval_tree_begin;

    ruby_eval_tree_begin = 0;
    if (beg_tree) {
	rb_eval(self, beg_tree);
    }

    if (!node) return Qnil;
    return rb_eval(self, node);
}
