Look at perlsub: &subname(); will disable prototype-checking for that call (now prototypes aren't used much in perl, for good reasons, but if they're there, you'll probably don't want to skip the checks).

Also, if you forget the parenthesis and call the sub as &subname; you will forward your current @_ array to that call. In other words, you will pass on your current arguments - not call it without arguments.

Instead of doing that, you should probably always write subname( args ) (i.e. with parenthesis and without the ampersand). It's the only way to call a subroutine that doesn't have any hidden snags. Generally, you'll only use the & sygil if you want to take references to named subroutines or for goto &subroutine which is only useful in very specific cases.