Ejemplo
<vxml version="1.0" application="carstore.vxml">
<var name="car" expr="'gremlin'"/ >
<var name="interior" expr="'vinyl'" />
<assign name="interior" expr="'leather'" />
<goto next="cars.vxml#sayCar" />
<var name="color" expr="'blue'" />
You want a <value expr="color" />
<value expr="car" /> with
<value expr="interior" /> seats.