CODE (br)
L1 BSET ( used in ?br and loop )
PC ORG @ 0x3d + ! ( stable ABI JP )
    E 0 IY+ LDrIXY, D 0 LDri,
    7 E BIT, IFNZ, D DECr, THEN,
    DE ADDIYd,
;CODE
CODE (?br)
PC ORG @ 0x41 + ! ( stable ABI JP )
    HL POP,
    HLZ,
    JRZ, L1 BWR ( br + 1. False, branch )
    ( True, skip next byte and don't branch )
    IY INCd,
;CODE