Return nothing from a CoffeeScript function

test.coffee

# Everything is an Expression
->
 greeting = 'Hi CoffeeScripter'

# Expect it's undefined
->
 greeting = 'Hi CoffeeScripter'
 return undefined

test.js

(function() {
  (function() {
    var greeting;
    return greeting = 'Hi CoffeeScripter';
  });
  (function() {
    var greeting;
    greeting = 'Hi CoffeeScripter';
  });
}).call(this);

You can do the same by just saying "return" (without "undefined").

Is there a global setting/configure to avoid writing "return"? The programmer can control the "return". I mean that return when we write it??