The following works for 5.8.0 on RH9 threaded.

In Foo.pm
                                       
package Foo;
 
use strict;
use warnings;
 
use Exporter;
 
our @ISA  = qw( Exporter );
our @EXPORT_OK = qw( foo );
 
sub foo { print "Foo\n"; }
 
1;

----------

In Bar.pm

package Bar;
 
use strict;
use warnings;
 
use Foo qw( foo );
our @ISA = qw( Foo );
 
sub bar { foo() }
 
1;

----------

In test.pl

#!/usr/bin/perl
 
use strict;
use warnings;
 
use Bar;
 
Bar::foo();
Bar::bar();
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*shrugs*