Question

Namespace or package are same? I use Perl where we only have packages. I know there are other programming languages that also include modules.

What’s the difference?

Answer 1

Namespace is a general computing term meaning a container for a distinct set of identifiers. The same identifier can appear independently in different namespaces and refer to different objects, and a fully-qualified identifier which unambiguously identifies an object consists of the namespace plus the identifier.

Perl implements namespaces using the package keyword.

A Perl module is a different thing altogether. It is a piece of Perl code that can be incorporated into any program with the use keyword. The filename should end with .pm – for Perl Module – and the code it contains should have a package statement using a package name that is equivalent to the file’s name, including its path. For instance, a module written in a file called My/Useful/Module.pm should have a package statement like package My::Useful::Module.

What you may have been thinking of is a class which, again, is a general computing term, this time meaning a type of object-oriented data. Perl uses its packages as class names, and an object-oriented module will have a constructor subroutine – usually called new – that will return a reference to data that has been blessed to make it behave in an object-oriented fashion. By no means all Perl modules are object-oriented ones: some can be simple libraries of subroutines.