10 LET t$="PACK MY BOX WITH FIVE DOZEN LIQUOR JUGS"
20 PRINT t$''
30 LET key=RND*25+1
40 LET k=key: GO SUB 1000: PRINT t$''
50 LET k=26-key: GO SUB 1000: PRINT t$
60 STOP
1000 FOR i=1 TO LEN t$
1010 LET c= CODE t$(i)
1020 IF c<65 OR c>90 THEN GO TO 1050
1030 LET c=c+k: IF c>90 THEN LET c=c-90+64
1040 LET t$(i)=CHR$ c
1050 NEXT i
1060 RETURN