our is not a declaration. It's different to local and my. Yes, it's confusing.

Have you tried it? For example:

1.pl

#!/usr/bin/perl
use warnings;
use strict;

our $x = 12;
require './2.pl';
print "Done\n";
[download]

2.pl

#!/usr/bin/perl
use warnings;
use strict;

our $x;

print $x, "\n";
[download]

Calling 1.pl:

12
Done
[download]