title: Array action is done on original array, not on copy
body: <p>I have an array like this:</p>
  
  <pre><code>@array_a = ["total", nil, 85.35, 85.97, 85.97, 0, 0, 0, 0, 0, 0, 0, 0, 0, nil]
  </code></pre>
  
  <p>I want <code>@array_b</code> to be like <code>@array_a</code> but without the first two elements ,and <code>@array_a</code> to remain as is. I assigned the first array to a second array, and removed some elements there:</p>
  
  <pre><code>@array_b = @array_a
  @array_b.shift
  @array_b.shift
  </code></pre>
  
  <p>Both <code>@array_a</code> and <code>@array_b</code> miss the first two elements:</p>
  
  <pre><code>[85.35, 85.97, 85.97, 0, 0, 0, 0, 0, 0, 0, 0, 0, nil]
  </code></pre>
  
  <p>How can I let <code>@array_a</code> be unchanged after manipulating <code>@array_b</code>?</p>