title: Change value of currently iterated element in list
body: <p>problem:
  when you use construction</p>
  
  <pre><code>for a in _list_:
      print a
  </code></pre>
  
  <p>it prints every item in array. But you can't alter array. Is it possible to alter value of array (something like a=123, but that ain't working)
  I know it's possible (for example in while loop), but I want to do it this way (more elegant)</p>
  
  <p>In PHP it would be like</p>
  
  <pre><code>foreach ($array as &amp;$value) {
      $value = 123;
  }
  </code></pre>
  
  <p>(because of <code>&amp;</code> sign, is passed as reference)</p>