That definitely sounds like a second stack to me...

```php
$m = new Mustache_Engine([
    'partials' => [
        'include' => '{{$ var }}var in include{{/ var }}'
    ],
]);

$tpl = '{{< include }}{{$ var }}var in template{{/ var }}{{/ include }}';
echo $m->render($tpl, ['var' => 'fail']);
```