Ant macrodef: Is there a way to get the contents of an element parameter?

I'm trying to debug a macrodef in Ant. I cannot seem to find a way to display the contents of a parameter sent as an element.

<project name='debug.macrodef'>
  <macrodef name='def.to.debug'>
    <attribute name='attr' />
    <element name='elem' />
    <sequential>
      <echo>Sure, the attribute is easy to debug: @{attr}</echo>
      <echo>The element works only in restricted cases: <elem /> </echo>
      <!-- This works only if <elem /> doesn't contain anything but a
           textnode, if there were any elements in there echo would
           complain it doesn't understand them. -->
    </sequential>
  </macrodef>

  <target name='works'>
    <def.to.debug attr='contents of attribute'>
      <elem>contents of elem</elem>
    </def.to.debug>
  </target>

  <target name='does.not.work'>
    <def.to.debug attr='contents of attribute'>
      <elem><sub.elem>contents of sub.elem</sub.elem></elem>
    </def.to.debug>
  </target>
</project>

Example run:

$ ant works
...
works:
 [echo] Sure, the attribute is easy to debug: contents of attribute
 [echo] The element works only in restricted cases:  contents of elem
...

$ ant does.not.work
...
does.not.work:
 [echo] Sure, the attribute is easy to debug: contents of attribute

BUILD FAILED
.../build.xml:21: The following error occurred while executing this line:
.../build.xml:7: echo doesn't support the nested "sub.elem" element.
...

So I guess I need either a way to get the contents of the <elem /> into a property somehow (some extended macrodef implementation might have that), or I need a sort of <element-echo><elem /></element-echo> that could print out whatever XML tree you put inside. Does anyone know of an implementation of eith