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
state, meaning that it is
only valid within a lexical scope. Unlike
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
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);
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
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
our declaration in the same package, in the same scope, is
our declaration may also have a list of attributes associated
The exact semantics and interface of TYPE and ATTRS are still
evolving. TYPE is currently bound to the use of the
and attributes are handled using the
pragma, or, starting
from Perl 5.8.0, also via the
Private Variables via my() in perlsub for details, and fields,
attributes, and Attribute::Handlers.
Note that with a parenthesised list,
undef can be used as a dummy
placeholder, for example to skip assignment of initial values: