title: Set a value on a multi level array
body: <p><code>dump(item.url.options.query)</code></p>
  
  <p>returns: <em>array (size=0)</em></p>
  
  <p><code>{% set item = item|merge({'ref': 'xyz'}) %}</code></p>
  
  <p>returns: no error, <em>item</em> is now set</p>
  
  <p><code>{% set item.url.options.query = item.url.options.query|merge({'ref': 'xyz'}) %}</code></p>
  
  <p>errors: <em>Twig_Error_Syntax: Unexpected token 'punctuation'; of value '.'</em></p>
  
  <p>How do I set the array index <em>item.url.options.query</em>?</p>