title: find and remove words matching a substring in a sentence
body: <p>Is it possible to use regex to find all words within a sentence that contains a substring?</p>
  
  <p>Example:</p>
  
  <pre><code>var sentence = "hello my number is 344undefined848 undefinedundefined undefinedcalling whistleundefined";
  </code></pre>
  
  <p>I need to find all words in this sentence which contains 'undefined' and remove those words. </p>
  
  <pre><code>Output should be "hello my number is ";
  </code></pre>
  
  <p>FYI - currently I tokenize (javascript) and iterate through all the tokens to find and remove, then merge the final string. I need to use regex. Please help.</p>
  
  <p>Thanks!</p>