code: public Object evaluate(Element m, TaskRequest req) {
  
          // Assertions.
          if (m == null) {
              String msg = "Argument 'm [Element]' cannot be null.";
              throw new IllegalArgumentException(msg);
          }
  
          return evaluate(compileTask(m), req);
  
      }
docs: Invokes the script defined by the specified element with the specified
  <code>TaskRequest</code> and returns the <code>RETURN_VALUE</code>.
  
  @param m An <code>Element</code> that defines a Task.
  @param req A <code>TaskRequest</code> prepared externally.
  @return The <code>RETURN_VALUE</code> of the specified task.