our has lexical scope.

c:\@Work\Perl\monks>perl -wMstrict -le
"{ package Foo;
   our $test = 12345;
   }
 ;;
 { package Bar;
   print 'fully qualified: ', $Foo::test;
   }
"
fully qualified: 12345
[download]

BTW: Perl 5.14 introduced the neater (IMHO)  package NAMESPACE BLOCK syntax, so the code above could now look like

package Foo {
    our $test = 12345;
    }

package Bar {
    print 'fully qualified: ', $Foo::test;
    }
[download]

Update: Note that package also has lexical scope!