VMS Help MACRO, VAX MACRO Assembler, Directives, .MEXIT  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    Terminates a macro expansion before the end of the macro.

      .MEXIT

    Termination is the same as if .ENDM  were encountered.  .MEXIT is
    useful  in  conditional  expansion  of macros because it bypasses
    the complexities of nested conditional directives and alternate
    assembly paths.