It's not a "makes sense" thing, it is a "what Perl does thing". Parameters to subroutines are passed in the special array @_ - that's what Perl does.

Go back and read the perlsub link that ikegami gave. That is pretty fundamental and important stuff to understand about how Perl goes about business. Take special note that array and hash parameters are flattened - look for the description of that process. There is a lot to understand about how Perl manages parameter passing!