title: Sorting an array by two values
body: <p>Suppose I have</p>
  
  <pre><code>an_array = [[2, 3], [1, 4], [1, 3], [2, 1], [1, 2]]
  </code></pre>
  
  <p>I want to sort this array by the first value of each inner array, and then by the second (so the sorted array should look like this: <code>[[1, 2], [1, 3], [1, 4], [2, 1], [2, 3]]</code>)</p>
  
  <p>What's the most readable way to do this?</p>