package Foo;
use base 'Exporter';
@EXPORT = "func";

sub func { return "Foo" }
##</code><code>##

package Bar;
use base 'Exporter';
@EXPORT = "func";

sub func { return "Bar" }
##</code><code>##

[matt@blue 478146] cat func.pl 
package func;
use Foo;
use Bar;
print func();
[matt@blue 478146] perl -l func.pl 
Bar

##</code><code>##

[matt@blue 478146] cat meth.pl 
package meth;

use base 'Foo';
use base 'Bar';

sub new { bless {}, __PACKAGE__ }
$o = new meth;
print $o->func;
[matt@blue 478146] perl -l meth.pl 
Foo