<document source="test data">
    <section ids="if-test" names="if test">
        <title>
            If Test
        <paragraph>
            Check out if directive in substitution definitions.
        <system_message level="1" line="6" source="test data" type="INFO">
            <paragraph>
                No directive entry for "if" in module "Text::Restructured::Directive".
                Trying "if" as canonical directive name.
        <substitution_definition names="empty">
        <substitution_definition names="nonempty">
            This text should be substituted.
        <paragraph>
            A paragraph. \n\
            <substitution_reference refname="empty">
                empty
            <substitution_reference refname="nonempty">
                nonempty
