Is there any way to "overload" two macrodefs in ant?

Question

I want to implement a <macrodef/> that can be called in two ways: With a single file parameter, or with a <fileset/>:

<macrodef name="sqlplus">
    <attribute name="file"/>
    <sequential>
        <!-- there be dragons, here -->
    </sequential>
</macrodef>

<macrodef name="sqlplus">
    <element name="files"/>
    <sequential>
        <for param="file">
            <path>
                <files/>
            </path>
            <sequential>
                <!-- call the other macro -->
                <sqlplus file="@{file}"/>
            </sequential>
        </for>
    </sequential>
</macrodef>

This doesn't seem to work. Is there any trick I can use to implement "quasi"-overloading? Or do I have to rename one of the macrodefs? I know I could write this, and check if the arguments are set (e.g. using ant-contrib):

<macrodef name="sqlplus">
    <attribute name="file"/>
    <element name="files" optional="yes"/>
    <!-- ... -->
</macrodef>

But there is no way to make an <attribute/> optional.