Page headers and footers belong to page style definitions (i.e. master pages). So an object that belong to a page header is defined in the "styles" part of the ODF container, and not in the "content" part (which is the default part unless the part option is not provided).
A table whose name is "TabHead" can be retrieved with getTable("TabHead"), but the context should be "styles" instead of "content". Ex:
$doc = odfDocument(file => "myfile.odt", part => "styles");
$table = $doc->getTable("TabHead");
Have a look at the "Dealing with styles an content" section in the OpenOffice::OODoc::Intro page for details regarding applications that need access to more than one document part in the same session (typically styles and content).
