title: Match a single occurrence of a string in a sentence using regEx
body: <p>If a sentence says </p>
  
  <blockquote>
    <p>"Hello Hello"</p>
  </blockquote>
  
  <p>the test should return false, but if its something like </p>
  
  <blockquote>
    <p>"Hello Jhon"</p>
  </blockquote>
  
  <p>it returns true.</p>
  
  <p>I thought this is all i had to do <code>/(hello){1}/</code></p>