loop1.0

loop [ commands ]

Repeats the commands forever, or until the enclosing procedure exits through use of the stop or report commands.

to move-to-world-edge  ;; turtle procedure
  loop [
    if not can-move? 1 [ stop ]
    fd 1
  ]
end

In this example, stop exits not just the loop, but the entire procedure.

Note: in many circumstances, it is more appropriate to use a forever button to repeat something indefinitely. See Buttons in the Programming Guide.