From language/variables

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our variables work just like my variables, except that they also introduce an alias into the symbol table.

module M {
    our $Var;
    # $Var available here 
}
 
# Available as $M::Var here.

In order to create more than one variable with package scope, at the same time, surround the variables with parentheses:

our ( $foo, $bar );

see also declaring a list of variables with lexical or package scope.