title: awk extract multiple groups from each line
body: <p>How do I perform action on all matching groups when the pattern matches multiple times in a line?</p>
  
  <p>To illustrate, I want to search for <code>/Hello! (\d+)/</code> and use the numbers, for example, print them out or sum them, so for input</p>
  
  <pre><code>abcHello! 200 300 Hello! Hello! 400z3
  ads
  Hello! 0
  </code></pre>
  
  <p>If I decided to print them out, I'd expect the output of</p>
  
  <pre><code>200
  400
  0
  </code></pre>