title: Mule variable declaration using set-payload vs expression component
body: <p>From this SO question <a href="https://stackoverflow.com/questions/23294001/mule-expression-variable-scope">Mule expression variable scope</a>, I understood that:</p>
  
  <ul>
  <li>variables declared using set-payload are like instance variables.</li>
  <li>variables defined in expression component are like method local variables.</li>
  </ul>
  
  <p>Is my understanding correct? How do we access variables inside expression component?</p>