All data not between specified begin and end tag pairs will be
stripped from the HTML before the text is extracted (i.e. links are
unaffected). These are simple strings, not patterns or REX
expressions, and the case is ignored. This is useful for extracting
prime interest areas of HTML pages without the surrounding
boilerplate. Tag pairs should not nest nor overlap in documents.
Documents with no begin tag will be unaffected. Documents with no end
tag after the last begin tag will still keep HTML from the last begin
tag to end of document.