How to have Ant/build.xml print a setting?

I'm working with Ant from the command line with Android. <sdk>/tools/ant//build.xml has lines like the following:

<!-- clean target -->
<target name="clean" depends="-setup, -pre-clean"
        description="Removes output files created by other targets.">
    <delete dir="${out.absolute.dir}" verbose="${verbose}" />
    <delete dir="${gen.absolute.dir}" verbose="${verbose}" />
...

I searched through the XML file, but I only found three usage of the word print (printseeds, printusage and printmapping). So print does not appear to be the way to print values.

How do I add a statement to print out.absolute.dir and gen.absolute.dir?