title: Scheme: change value of an element in a list
body: <p>I hate using SO as a way to find simple functions, but I really can't find a function like this anywhere:    </p>
  
  <p>Given a list (1 2 3 4 5), I'd like the equivalent of (PHP's, Perl's, Python's)  </p>
  
  <pre><code>$a = array(1, 2, 3, 4, 5);   
  $a[3] = 100;  
  </code></pre>
  
  <p>Which results in (1 2 3 100 5)</p>
  
  <p>Thanks!</p>