CODE ROT ( a b c -- b c a )
    HL POP, ( C ) DE POP, ( B ) IY POP, ( A ) chkPS,
    DE PUSH, ( B ) HL PUSH, ( C ) IY PUSH, ( A )
;CODE
CODE DUP ( a -- a a )
    HL POP, chkPS,
    HL PUSH, HL PUSH,
;CODE
CODE ?DUP
    HL POP, chkPS,
    HL PUSH,
    HLZ, IFNZ, HL PUSH, THEN,
;CODE
CODE DROP ( a -- )
    HL POP,
;CODE