DO DNEGATE DOER
DO .. LOOP ( end start -- )  
smart-word ansi .6.1.1240 <CORE>
pushes $end and $start onto the return-stack ( >R ) and starts a control-loop that ends with LOOP or +LOOP and may get a break-out with LEAVE . The loop-variable can be accessed with I

reference: p4_do in ../src/core.c:0940, export CS DO