scope - What is the difference between 'my' and 'our' in Perl?

Question

I know what my is in Perl. It defines a variable that exists only in the scope of the block in which it is defined. What does our do?

How does our differ from my?

Answer 1

Great question: How does our differ from my and what does our do?

In Summary:

Available since Perl 5, my is a way to declare non-package variables, that are:

• private
• new
• non-global
• separate from any package, so that the variable cannot be accessed in the form of $package_name::variable.

On the other hand, our variables are package variables, and thus automatically:

• global variables
• definitely not private
• not necessarily new
• can be accessed outside the package (or lexical scope) with the qualified namespace, as $package_name::variable.

Declaring a variable with our allows you to predeclare variables in order to use them under use strict without getting typo warnings or compile-time errors. Since Perl 5.6, it has replaced the obsolete use vars, which was only file-scoped, and not lexically scoped as is our.

For example, the formal, qualified name for variable $x inside package main is $main::x. Declaring our $x allows you to use the bare $x variable without penalty (i.e., without a resulting error), in the scope of the declaration, when the script uses use strict or use strict "vars". The scope might be one, or two, or more packages, or one small block.