Separate variable assignment and usage into two expressions

---

examples/angular/assignment_and_expression.html

<script src="angular.min.js"></script>
<div ng-app>
  <div>
  Result
  {{ x + y }}
  </div>
  <div>
    Assignment:
    {{ x = 23; y= 19 }}
  </div>
  <div>
    Result
    {{ x + y }}
  </div>
</div>

Result 42
Assignment: 19
Result 42