       10 // LOOP sample program
       20 //
       30 i:=1
       40 LOOP
       50   LOOP
       60     i:+1
       70     EXIT WHEN i>10
       80   ENDLOOP
       90   EXIT WHEN i>20
      100 ENDLOOP
      110 //
      120 SYS assert, i=21
      130 //
      140 LOOP
      150   i:-1
      160   IF i=0 THEN EXIT
      170 ENDLOOP
      180 //
      190 SYS assert, i=0
      200 //
      210 PRINT "Ok"
