<project default="main">
  <target name="main"/>
  <macrodef name="mytask">
    <attribute name="attr1"/>
    <attribute name="attr2"/>
    <element name="antcall"/>
    <sequential>
      <echo message="attr1=@{attr2}">attr1=@{attr1}</echo>
    </sequential>
  </macrodef>
  <mytask attr1="" attr2="t">
    <antcall/>
  </mytask>
</project>