Just forget about prototypes. Perl does not need them in most cases. All agree that the Perl prototypes are one of the most misunderstood features of Perl. More specifically they are NOT made to give you the general ability to check whether correct paramaters have been provided to your sub. If you want to make sure correct parameters are given to your sub, you must include these tests inside your sub and these tests then work at run-time, not at compile-time (as in many bondage and discipline languages).
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
My blog: Imperial Deltronics