package Test;

use strict;
use warnings;

sub new{
    bless {},shift;
}

sub test{
    print "Hallo\n";
}

1;

#!/usr/bin/perl

use strict;
use warnings;
use lib qw(.);
use Test;

my $test = Test->new();
$test->test();

no warnings 'redefine';
*Test::test = sub{print "Welt\n"};
$test->test();