Sams Teach Yourself Perl in 24 Hours

Creating and Calling Subroutines

You create user-defined subroutines in Perl by using the following syntax:

sub subroutine_name {
    statement1;
    :
    statementx;
}

Subroutine names in Perl follow the same naming conventions as scalars, arrays, and hashes outlined in Hour 2, "Perl's Building Blocks: Numbers and Strings." Subroutine names can have the same names as existing variables. However, you should avoid creating subroutine names with the same names as Perl's built-in functions and operators. Creating two subroutines with the same name in Perl causes Perl to emit a warning if warnings are enabled; otherwise, the second definition causes the first to be forgotten.

When the subroutine is invoked, the subroutine's code is run and any return value ...