Since there was just a golf for factorials, I figured that doing one for the number of ways to select M objects from a set of N objects without repetition might be appropriate.
Basically, if I have a set of 4 cards, how many ways can I select a hand of 1 card from the set without repeating myself? The answer is obviously 4. Now if I have a hand size of 2 how many ways are there? The answer is 6, but it is less obvious.
The general solution is defined by the function:
Choose(M, N) = M!

N! * (M  N)!
Where M is the size of the set and N is the number of cards to select. And M! is the factorial of M. See Golf: Factorials for more info.
The following are test cases that you can use:
M  N  Answer  Notes 
52  5  2598960  Number of 5 card hands in a deck of 52 cards 
52  7  133784560  Number of 7 card hands in a deck of 52 cards 
52  13  635013559600  Number of 7 card hands in a deck of 52 cards

52  52  1  Number of ways to select a hand size of 1 from a 52 card deck 
The interface for the resulting code should be:
print c($m, $n);
If you want to define a factorial subroutine that should be included in the size of the code.
ben
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