~>cat x.pl
use y;
use z;
z_sub();

~>cat y.pm
package y;
sub global_sub {
    print "global_sub working!"
}
1

~>cat z.pm
package z;
use Exporter 'import';
our @EXPORT = qw(z_sub);
sub z_sub {
    global_sub();
}
1

~>perl x.pl
Undefined subroutine &z::global_sub called at z.pm line 5.


##</code><code>##

~>cat x.pl
use y;
use z;
z_sub();

~>cat y.pm
package y;
sub G::global_sub {
    print "global_sub working!"
}
1

~>cat z.pm
package z;
use Exporter 'import';
our @EXPORT = qw(z_sub);
sub z_sub {
    G::global_sub();
}
1

~> perl x.pl
global_sub working!