<p xmlns:z="http://xml.zope.org/namespaces/tal">
  <span z:define="local x str:hello brave new world">
    <span z:content="text local:x">outer variable x, first appearance</span>
    <span z:define="local x str:goodbye cruel world">
      <span z:content="text local:x">inner variable x</span>
    </span>
    <span z:content="text local:x">outer variable x, second appearance</span>
  </span>
</p>