VMS Help CC, Messages, UNDEFESCAP  *Conan The Librarian (sorry for the slow response - running on an old VAX)

 Message        An undefined escape sequence was encountered; the
                backslash is being ignored.

 Description    The character or characters following a backslash do
                not form a valid escape sequence.  The compiler will
                ignore the backslash.

 User Action    Correct the escape sequence.