What is a Module

What is a Module

Has a filename ending with '.pm' and a package name to match If the filename is in a lower directory, the package name uses '::' for the directory separator

The Barest of Modules

• package gives the name of the module
• The filename would be Sample/Module.pm and the Sample directory will live in one of the directories listed in @INC

use Exporter

• The Exporter module makes the changes to symbol tables to export functions and variables from one package to another

use vars

• These are package variables needed to make Exporter happy
• $VERSION is also known as $Sample::Module::VERSION

$VERSION

• Required variable
• Should be a real number like 0.1 or 2.9996
• Should not be like LINUX kernal numbering 2.2.4 with extra periods

@ISA

• Modules to inherit variables, methods, and functions from

@EXPORT


 

 

Functions and Variables here are exported by default. They will pollute the name space of the package that calls this module and can be called without a package name Give a Hoot, Don't Pollute. Only export by default those things that really need it.

@EXPORT_OK

• Functions and Variables here are exported only if requested.
• Otherwise they can still be used, but you must give the full name like $Sample::Module::Foo
• my variables can not be exported, must use vars

%EXPORT_TAGS


 

 

Pre-defined groups of things to export. All functions and variables included must also be in either @EXPORT or @EXPORT_OK.

@EXPORT_FAIL


 

 

List of things to never ever export

1

• All modules (and required files) need to return a true value. The simplest way to guarantee a true value is to end the module with a "1;", which is true.

__END__

The "__END__" tells Perl to ignore anything after it. If you have documentation or retired functions you can't yet throw away, it is easy to leave them after the "__END__" where they will do no harm.