 line starting pod, such as &#39;=head&#39;
    POD            - pod documentation text
    POD_END        - last line of pod section, &#39;=cut&#39;
    HERE           - text of here-document
    HERE_END       - last line of here-doc (target word)
    FORMAT         - format section
    FORMAT_END     - last line of format section, &#39;.&#39;
    DATA_START     - __DATA__ line
    DATA           - unidentified text following __DATA__
    END_START      - __END__ line
    END            - unidentified tex