As a general rule don't use prototypes unless there is a good reason for it such as passing in several arrays without them getting flattened into one @_. And even then passing references to the arrays is probably a more clear solution.
I see no merit in adding a prototype definition of ($$).
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