About Perl Pragmas, Modules, and CPAN – the Comprehensive Perl Archive Network.
Basics on manipulating files and directories with Perl.
Basic Regular Expressions for Perl
Introduction
Subroutines are user-created functions that execute a block of code at any given place in your program. It is a best practice, however, to aggregate them all either at the beginning or the end the main program.
Subroutine declarations initiate with the key word “sub” . Conventionally, subroutine names are all lowercase characters
sub NAME (PROTOTYPE) [...]