sgml-tag-text-p

sgml-tag-text-p is a compiled Lisp function in `sgml-mode.el'.

(sgml-tag-text-p START END)

Return non-nil if text between START and END is a tag.
Checks among other things that the tag does not contain spurious
unquoted < or > chars inside, which would indicate that it
really isn't a tag after all.