DIM perms$(22), miss&(4)
      perms$() = "ABCD", "CABD", "ACDB", "DACB", "BCDA", "ACBD", "ADCB", \
      \  "CDAB", "DABC", "BCAD", "CADB", "CDBA", "CBAD", "ABDC", "ADBC", \
      \  "BDCA", "DCBA", "BACD", "BADC", "BDAC", "CBDA", "DBCA", "DCAB"

      FOR i% = 0 TO DIM(perms$(),1)
        FOR j% = 1 TO DIM(miss&(),1)
          miss&(j%-1) EOR= ASCMID$(perms$(i%),j%)
        NEXT
      NEXT
      PRINT $$^miss&(0) " is missing"
      END