100 CLS : rem  10 HOME for Applesoft BASIC
110 FOR N = 1 TO 7
120   READ S$
130   IF S$ = "" THEN PRINT"(EMPTY)";: GOTO 150
140   PRINT S$;
150   PRINT TAB(9);
160   GOSUB 190
170 NEXT N
180 END
190 S = 0
200 FOR K = 1 TO LEN(S$)
210   C$ = MID$(S$,K,1)
220   IF C$ = "[" THEN S = S+1
230   IF C$ = "]" THEN S = S-1
240   IF S < 0 THEN PRINT "NOT OK": RETURN
250 NEXT K
260 IF S = 0 THEN PRINT "  OK": RETURN
270 PRINT "NOT OK"
280 RETURN
290 DATA "", "[]", "][", "[][]", "][][", "[[][]]", "[]][[]"