title: How to properly split this list of strings?
body: <p>I have a list of strings such as this : </p>
  
  <pre><code>['z+2-44', '4+55+z+88']
  </code></pre>
  
  <p>How can I split this strings in the list such that it would be something like</p>
  
  <pre><code>[['z','+','2','-','44'],['4','+','55','+','z','+','88']]
  </code></pre>
  
  <p>I have tried using the <code>split</code> method already however that splits the 44 into 4 and 4, and am not sure what else to try.</p>