eval.c:5713
VALUE
rb_obj_instance_eval(argc, argv, self)
    int argc;
    VALUE *argv;
    VALUE self;
{
    VALUE klass;

    if (rb_special_const_p(self)) {
	klass = Qnil;
    }
    else {
	klass = rb_singleton_class(self);
    }

    return specific_eval(argc, argv, klass, self);
}
