title: Use grep to remove words from dictionary whose roots are already present
body: <p>I am trying to write a random passphrase generator. I have a dictionary with a bunch of words and I would like to remove words whose root is already in the dictionary, so that a dictionary that looks like: </p>
  
  <pre><code>ablaze
  able
  abler
  ablest
  abloom
  ably
  </code></pre>
  
  <p>would end up with only</p>
  
  <pre><code>ablaze
  able
  abloom
  ably
  </code></pre>
  
  <p>because abler and ablest contain able which was previously used.</p>
  
  <p>I would prefer to do this with grep so that I can learn more about how that works. I am capable of writing a program in c or python that will do this.</p>