title: reference matches in a string gsub regexp
body: <p>Say I have a string like this</p>
  
  <pre><code>"some3random5string8"
  </code></pre>
  
  <p>I want to insert spaces after each integer so it looks like this</p>
  
  <pre><code>"some3 random5 string8"
  </code></pre>
  
  <p>I specifically <strong>want to do this using <code>gsub</code></strong> but I can't figure out how to access the characters that match my regexp. </p>
  
  <p>For example:</p>
  
  <pre><code>temp = "some3random5string8"
  temp.gsub(/\d/, ' ')  # instead of replacing with a ' ' I want to replace with
                        # matching number and space
  </code></pre>
  
  <p>I was hoping there was a way to reference the regexp match. Something like <code>$1</code> so I could do something like <code>temp.gsub(/\d/, "#{$1 }")</code> (note, this does not work)</p>
  
  <p>Is this possible?</p>