# file bar.pl
use strict;

{
    package Bar;
    our $foo; # package variable $Bar::foo created
    print __FILE__,' ',__LINE__,' ',__PACKAGE__,":: \$foo is '$foo'\n";
} # end of scope

package Foo;
our $foo; # package variable $Foo::foo initialized in 'foo.pl'
print __FILE__,' ',__LINE__,' ',__PACKAGE__,":: \$foo is '$foo'\n";

package Bar;
print __FILE__,' ',__LINE__,' ',__PACKAGE__,":: \$foo is '$foo'\n";