title: Match phone number not preceded by text
body: <p>I try to use negative lookbehind regex to match phone numbers not preceded by text:</p>
  
  <pre><code>Tel (123) 456-7890
  </code></pre>
  
  <p>What I have so far matches both cases, with and without preceding text, 
  not sure why.</p>
  
  <pre><code>(?&lt;!Tel )(\+\d{1,2}\s)?\(?\d{3}\)?[\s.-]\d{3}[\s.-]\d{4}
  </code></pre>
  
  <p>Thanks</p>