10 PRINT CHR$(147): REM CLEAR SCREEN
20 FOR N=1 TO 7
30   READ S$
40   IF S$="" THEN PRINT"(EMPTY)";: GOTO 60
50   PRINT S$;
60   PRINT TAB(20);
70   GOSUB 1000
80 NEXT N
90 END
100 REM ********************************
1000 S = 0
1010 FOR K=1 TO LEN(S$)
1020   C$ = MID$(S$,K,1)
1030   IF C$="[" THEN S = S+1
1040   IF C$="]" THEN S = S-1
1050   IF S<0 THEN PRINT "NOT OK": RETURN
1060 NEXT K
1070 IF S=0 THEN PRINT "OK": RETURN
1090 PRINT "NOT OK"
1100 RETURN
2000 DATA , [], ][, [][], ][][, [[][]], []][[]