Math::Combinatorics will not do the trick: it will give you
all the permutations of an array or list, but cannot do
nPk where
n < k. Use
Algorithm::Permute for that.
CountZero
A program should be light and agile, its subroutines connected like a string of pearls. The spirit and intent of the program should be retained throughout. There should be neither too little or too much, neither needless loops nor useless variables, neither lack of structure nor overwhelming rigidity." - The Tao of Programming, 4.1 - Geoffrey James