title: regular expression to extract middle section of string
body: <p>What could be the regex to extract 58392 from this example.</p>
  
  <p>the number between the colon and hash would be variable length</p>
  
  <pre><code>sip:58392#7638500@10.10.10.10
  </code></pre>
  
  <p>I tried conbinations of like this but no luck <code>sip:(.*?)#/\1/</code></p>