FOR len = 0 TO 18 STEP 2

    str$ = ""
    DOTIMES len
        str$ = str$ & CHR$(IIF(RANDOM(2) = 0, 91, 93))
    DONE

    status = 0
    FOR x = 1 TO LEN(str$)
        IF MID$(str$, x, 1) = "[" THEN
            INCR status
        ELSE
            DECR status
        FI
        IF status < 0 THEN BREAK
    NEXT

    IF status = 0 THEN
        PRINT "OK: ", str$
    ELSE
        PRINT "BAD: ", str$
    ENDIF
NEXT