Use the arithmetic shift operator (@)  to perform left and right
    arithmetic shifts of arithmetic quantities. The first argument
    is shifted left or right by the number of bit positions that
    you specify in the second argument. If the second argument is
    positive, the first argument is shifted left and the low-order
    bits are set to zero. If the second argument is negative, the
    first argument is shifted right and the high-order bits are set
    to the value of the original high-order bit (the sign bit). For
    example:

            .LONG   ^B101@4              ; Yields 1010000 (binary)
            .LONG   1@2                  ; Yields 100 (binary)
    A = 4
            .LONG   1@A                  ; Yields 10000 (binary)
            .LONG   ^X1234@-A            ; Yields 123(hex)