title: Prolog "operator expected error" on predicate commands sequence
body: <p>This very simple Prolog example from my study material is giving me an "Operator Expected" error:</p>
  
  <pre><code>greet(alice):- 
          write(‘How are you doin, pal?’).
  greet(bob):- 
          write(‘Awfully nice to see you!’).
  </code></pre>
  
  <p>What an I missing ?</p>