title: How do I modify an array while I am iterating over it in Ruby?
body: <p>I'm just learning Ruby so apologies if this is too newbie for around here, but I can't work this out from the pickaxe book (probably just not reading carefully enough).
  Anyway, if I have an array like so:</p>
  
  <pre><code>arr = [1,2,3,4,5]
  </code></pre>
  
  <p>...and I want to, say, multiply each value in the array by 3, I have worked out that doing the following:</p>
  
  <pre><code>arr.each {|item| item *= 3}
  </code></pre>
  
  <p>...will not get me what I want (and I understand why, I'm not modifying the array itself).</p>
  
  <p>What I don't get is how to modify the original array from inside the code block after the iterator. I'm sure this is very easy.</p>