Perl in a Nutshell, 2nd Edition

Name

sub

Synopsis

sub name [proto] {block}
sub [proto] name
                  

Declares and defines a subroutine. name is the name given to the subroutine; block is the code that will be executed when the subroutine is called. Without block, this statement declares only a subroutine, which must be defined at a later point in your program. proto is a sequence of symbols that places constraints on the arguments that the subroutine will receive. See Section 4.7.