FLIPFLAG         Optimized XOR                                      Extension

    Optimized form of the XOR instruction that complements bits with
    shortest possible instruction. Use only if the resulting contents of
    the flags registers are unimportant.

    Example:    RECORD state  zone:4, chg:1, ins:1=1, bak:1=0, onoff:1
                ;...
                FLIPFLAG [ed_state],MASK ins