Thank you, for pointing me to the "factorial"
Note to self: Don't transfer mathematical/technical terms from German to English without consulting a dictionary first.
Also, would you be able to give example code for the subset iteration with Math::Combinatorics?
If there is an easy way to do so, it has escaped me.
The closest I saw in the docs was that example to generate: "Morse signals: diferent signals of 3 positions using the two symbols  and .".
Now Morse signals of length 3 are surely onetoone and onto the subsets of a 3 element set (set elements = pos in signal; element not/contained = dot/dash)
The given iteration using next_multiset and next_string is like computing 2**n as sum_{k=0..n} nCk
At least this is not trivial application of the modules methods.
