our makes a lexical alias to a package (i.e. global) variable of the same name in the current package for use within the current lexical scope.
our has the same scoping rules as my or state, meaning that it is only valid within a lexical scope. Unlike my and state, which both declare new (lexical) variables, our only creates an alias to an existing variable: a package variable of the same name.
This means that when
use strict 'vars'
is in effect, our lets you use a package variable without qualifying it with the
package name, but only within the lexical scope of the
our declaration. This applies immediately--even
within the same statement.
This works even if the package variable has not been used before, as package variables spring into existence when first used.
Because the variable becomes legal immediately under
use strict 'vars'
long as there is no variable with that name is already in scope, you can then
reference the package variable again even within the same statement.
If more than one variable is listed, the list must be placed in parentheses.
- our($bar, $baz);
An our declaration declares an alias for a package variable that will be visible across its entire lexical scope, even across package boundaries. The package in which the variable is entered is determined at the point of the declaration, not at the point of use. This means the following behavior holds:
Multiple our declarations with the same name in the same lexical scope are allowed if they are in different packages. If they happen to be in the same package, Perl will emit warnings if you have asked for them, just like multiple my declarations. Unlike a second my declaration, which will bind the name to a fresh variable, a second our declaration in the same package, in the same scope, is merely redundant.
An our declaration may also have a list of attributes associated with it.
The exact semantics and interface of TYPE and ATTRS are still evolving. TYPE is currently bound to the use of the fields pragma, and attributes are handled using the attributes pragma, or, starting from Perl 5.8.0, also via the Attribute::Handlers module. See Private Variables via my() in perlsub for details.
Note that with a parenthesised list, undef can be used as a dummy placeholder, for example to skip assignment of initial values: