I ran the code above and got this:
A,B,C,D,E,F
N,N,A,B,C,D,E,F
N,A,N,B,C,D,E,F
N,A,B,N,C,D,E,F
N,A,B,C,N,D,E,F
N,A,B,C,D,N,E,F
N,A,B,C,D,E,N,F
N,A,B,C,D,E,F,N
A,N,N,B,C,D,E,F
A,N,B,N,C,D,E,F
A,N,B,C,N,D,E,F
A,N,B,C,D,N,E,F
A,N,B,C,D,E,N,F
A,N,B,C,D,E,F,N
A,B,N,N,C,D,E,F
A,B,N,C,N,D,E,F
A,B,N,C,D,N,E,F
A,B,N,C,D,E,N,F
A,B,N,C,D,E,F,N
A,B,C,N,N,D,E,F
A,B,C,N,D,N,E,F
A,B,C,N,D,E,N,F
A,B,C,N,D,E,F,N
A,B,C,D,N,N,E,F
A,B,C,D,N,E,N,F
A,B,C,D,N,E,F,N
A,B,C,D,E,N,N,F
A,B,C,D,E,N,F,N
A,B,C,D,E,F,N,N
Is this what you wanted? What does that represent? How is that useful to you?
Needless to say, you always want use strict; use warnings; in your code.
