tt(ATEXIT) expects one argument. The argument is appended to the output
file. Note that this text is subject to character table translations etc..

An example using this function is the following. A document in the
LaTeX typesetting language requires tt(\end{document}) to occur at the end of
the document. To automatically append this string to the output file, the
following specification can be used:
        verb(
    ATEXIT(NOEXPAND(\end{document}))
        )
    Several tt(ATEXIT) lists can be defined. They are appended to the output
file in the bf(reverse) order of specification; i.e., the first tt(ATEXIT)
list is appended to the output file last. That means that in general the
tt(ATEXIT) text should be specified when a `matching' starting command is sent
to the output file; as in:
        verb(
    COMMENT(Start the LaTeX document.)
    NOEXPAND(\begin{document})
    
    COMMENT(Ensure its proper ending.)
    ATEXIT(\
        NOEXPAND(\end{document})\
    )
        )
