old_contents: # This program runs in an infinite loop (don't run unless you know how to stop it)
  # Hint: CTRL-C usually works
  while True:
      print('Hello world!')
  
new_contents: """Infinite loop
  
  This program runs in an infinite loop (don't run unless you know how to stop it!).
  
  Note:
      * CTRL-C usually works
  
  """
  
  
  def main():
      while True:
          print('Hello world!')
  
  
  # If P05_infiniteloop.py is run (instead of imported as a module), call
  # the main() function:
  if __name__ == '__main__':
      main()
  
subject: Update P05_infiniteloop.py added docstring and wrapped in main() function