( Core words )
( KEY and EMIT are not defined here. There're
  expected to be defined in platform-specific code. )

CODE EXECUTE
    DE POPqq,
    chkPS,
    JR, lblexec BWR      ( execute-B301 )

( a b c -- b c a )
CODE ROT
    HL POPqq, ( C ) DE POPqq, ( B ) BC POPqq, ( A )
    chkPS,
    DE PUSHqq, ( B ) HL PUSHqq, ( C ) BC PUSHqq, ( A )
;CODE