# Copyright (C) 2004-2007, The Perl Foundation.
# $Id: oofib.pl 21228 2007-09-12 19:23:12Z paultcochrane $

use strict;
use warnings;

package A;

sub fib {
    my $self = shift;
    my $n    = shift;
    return $n if ( $n < 2 );
    return $self->fibA( $n - 1 ) + $self->fibB( $n - 2 );
}

sub fibA {
    my $self = shift;
    my $n    = shift;
    return $n if ( $n < 2 );
    return $self->fib( $n - 1 ) + $self->fibB( $n - 2 );
}

package B;
@B::ISA = qw(A);
sub new { return bless {}, $_[0] }

sub fibB {
    my $self = shift;
    my $n    = shift;
    return $n if ( $n < 2 );
    return $self->fib( $n - 1 ) + $self->fibA( $n - 2 );
}

package main;

my $N = shift || 28;

my $b = B->new();

print "fib($N) = ", $b->fib($N), "\n";

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