package P;

sub new {
    my ($proto) = @_;
    my $self = {};
    bless $self => $proto;
}

sub foo {
    print "P: foo\n";
}

sub bar {
    print "P: bar\n";
}

package Pprime;

@Pprime::ISA = qw(P);

sub new {
    my ($proto) = @_;
    my $self = {};
    bless $self => ref($proto) || $proto;
}

package Q;

sub new {
    my ($proto) = @_;
    my $self = {};
    bless $self => $proto;
}

sub bar {
    my $self = shift;
    print "Q: bar\n";
    $self->SUPER::bar();
}

sub test {
    my $self = shift;
    $self->foo();
    $self->bar();
}

package Qprime;

@Qprime::ISA = qw(Q Pprime);

sub new {
    my ($proto) = @_;
    my $self = {};
    bless $self => ref($proto) || $proto;
}

package main;

my $obj = Qprime->new();
$obj->test();

##</code><code>##

P: foo
Q: bar
Can't locate object method "bar" via package "Q" (perhaps you forgot to load "Q"?) at ./demo.pl line 40.