SAMS Teach Yourself Perl in 24 Hours THIRD EDITION

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 that are the same as those of 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.

Here is an example of a subroutine:

 sub countdown { for ($i=10; $i>=0; $i--) ...