title: Cloning an array with its content
body: <p>I want to make a copy of an array, to modify the copy in-place, without affecting the original one. This code fails</p>
  
  <pre><code>a = [
    '462664',
    '669722',
    '297288',
    '796928',
    '584497',
    '357431'
  ]
  b = a.clone
  b.object_id == a.object_id # =&gt; false
  a[1][2] = 'X'
  a[1] #66X722
  b[1] #66X722
  </code></pre>
  
  <p>The copy should be different than the object. Why does it act like if it were just a reference?</p>