VMS Help RTL Routines, LIB$, LIB$ESTABLISH, Returns  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    OpenVMS usage:routine
    type:         procedure value
    access:       write only
    mechanism:    by reference

    Previous contents of SF$A_HANDLER (longword 0) of the caller's
    stack frame; zero if no handler existed.