( ex: L1 LBL! .. L1 @ RJMP, )
: LBL! ( l -- ) PC SWAP ! ;
( ex: L1 FLBL, .. RJMPOP L1 FLBL! )
: FLBL, ( l -- ) LBL! 0 A,, ;
: FLBL! ( op l -- )
    @ DUP PC -^ 1-  ( op l off )
    ROT 8 LSHIFT OR ( l op' )
    ( warning: l is a PC offset, not a mem addr! )
    SWAP 2 * ORG @ + ( op' addr ) ! ;