: (key)
_next C@ IF _next C@ 0 _next C! EXIT THEN
BEGIN _updsel UNTIL
_prevstat C@
0x20 ( BUTC ) OVER AND NOT IF DROP _sel C@ EXIT THEN
0x40 ( BUTA ) AND NOT IF 0x8 ( BS ) EXIT THEN
( If not BUTC or BUTA, it has to be START )
0xd _next C! _sel C@
;