10 REM DO/LOOP in all four shapes, plus ON and a multi-line IF block.
20 I# = 0
30 DO WHILE I# < 3
40   PRINT "WHILE " + I#
50   I# = I# + 1
60 LOOP
70 I# = 0
80 DO
90   PRINT "UNTIL " + I#
100   I# = I# + 1
110 LOOP UNTIL I# = 2
120 REM A condition already false runs no body at all.
130 DO WHILE 1 == 2
140   PRINT "NEVER SEEN"
150 LOOP
160 REM ON picks the nth target, one-based, and falls through past the end.
170 X# = 2
180 ON X# GOSUB 500, 600
190 X# = 7
200 ON X# GOTO 500, 600
210 PRINT "FELL THROUGH"
220 REM BEGIN/BEND makes an IF span lines.
230 IF I# = 2 THEN BEGIN
240   PRINT "IN BLOCK"
250 BEND
260 IF I# = 99 THEN BEGIN
270   PRINT "NEVER SEEN EITHER"
280 BEND
290 END
500 PRINT "SUB ONE"
510 RETURN
600 PRINT "SUB TWO"
610 RETURN