title: How to match all strings that has only one dot using regular expression
body: <p>I need to capture strings containing only one dot. String will mostly contains domain names like </p>
  
  <p>test.com, fun.test.com, lesh.test.com.</p>
  
  <p>I need to check only the first one and to ignore the string that has more than one dots.</p>
  
  <p>How can I do this using regex?</p>