title: Only extract those words from a list that include no repeating letters, using regex
body: <p>I have a large word list file with one word per line. I would like to filter out the words with repeating alphabets. </p>
  
  <pre><code>INPUT:
    abducts
    abe
    abeam
    abel
    abele
  
  OUTPUT:
    abducts
    abe
    abel
  </code></pre>
  
  <p>I'd like to do this using Regex (grep or perl or python). Is that possible?</p>