( a -- a a )
CODE DUP
    HL POPqq, chkPS,
    HL PUSHqq, HL PUSHqq,
;CODE

CODE ?DUP
    HL POPqq, chkPS,
    HL PUSHqq,
    HLZ, IFNZ, HL PUSHqq, THEN,
;CODE

( a -- )
CODE DROP
    HL POPqq,
;CODE