package pq;
use strict;
use warnings;

use constant {
    ONE => "1"
};

sub new {
    my ($class) = @_;

    bless {}, $class;
}

sub pr { print main::FO1; }
1;

##</code><code>##

use strict;
use warnings;
use pq;

use constant {
FO1 => "value"
};

print pq::ONE;   # Prints 1, working right.!

my $obj = new pq;
pq->pr();        # says 'print() on unopened filehandle FO1 at pq.pm line 28.'