LEAVE [symbol]

If a symbol name is not specified, then LEAVE leaves the innermost
repetitive DO statement by jumping to the statement after the END
statement for that loop. If a symbol name is specified, then LEAVE
leaves the innermost loop with that symbol as control (i.e. where the
DO statement specified that symbol) - this may involve leaving several
inner loops.  The specified symbol must match that in the DO
instruction literally, except that case is ignored.
  The LEAVE statement will not return from procedures or functions.
  If there is no suitable loop to leave within the current function or
procedure call, then an error results.

NOTE: LEAVE will not exit from a string being interpreted: it is an
      error to use LEAVE within INTERPRET unless the corresponding DO
      occurs there as well.