The argument concatenation operator, the apostrophe ('),
    concatenates a macro argument with constant text or another
    argument. Apostrophes can either precede or follow a formal
    argument name in the macro source.

    If an apostrophe precedes the argument name, the text before
    the apostrophe is concatenated with the actual argument when
    the macro is expanded. For example, if ARG1 is a formal argument
    associated with the actual argument TEST, then ABCDE'ARG1 is
    expanded to ABCDETEST.

    If an apostrophe follows the formal argument name, the actual
    argument is concatenated with the text that follows the
    apostrophe when the macro is expanded. The apostrophe itself
    does not appear in the macro expansion.

    To concatenate two arguments, separate the two formal arguments
    with two successive apostrophes. Two apostrophes are needed
    because each concatenation operation discards an apostrophe from
    the expansion.

    An example of a macro definition that uses concatenation follows:

            .MACRO CONCAT   A,B
    A''B:   .WORD 0
            .ENDM CONCAT

    Note that two successive apostrophes are used when concatenating
    the two formal arguments A and B.

    An example of a macro call and expansion follows:

            CONCAT  X,Y
    XY:     .WORD 0