author elements in tei headers

I have an XPath question, and more specifically, how can I determine the number of author elements found an a TEI header?

I would like to create summary files similar to the files created by the late Sebastian Rantz and found on GitHub. [1] I can easily determine the number of author elements found in an entire TEI file with a Perl-esque XPath statement similar to this:

  $parser->find( “//author" )->size

But I’d like to know how to limit the finding of author elements to only the teiheader or text elements. 

[1] see, for example - https://github.com/textcreationpartnership/A00002

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Eric Morgan