title: Regular expression for double parentheses
body: <p>De regular expression below is working fine to find all curly brackets ( '{' and '}' ). But I need to find double parentheses ( '((' and '))' )</p>
  
  <pre><code>/\{(((?&gt;[^\{\}]+)|(?R))*)\}/x
  </code></pre>
  
  <p>Anyone who knows how to translate the above regular expression to that?
  It's necassary to find parentheses on multilevel. So It needs to find parentheses between parentheses as well.</p>