package MyClassA;

use strict;
use warnings 'all';

sub new {
    my $classname = shift;
    my $self = {};
    bless($self, $classname);
    my %extras = @_;
    @$self{keys %extras} = values %extras;
    return $self;
}

sub TO_JSON {
    my $self = shift;
    return { %{$self} };
}

sub setClassB {
    my $self = shift;
    $self->{MY_CLASS_B} = shift;
}

sub getClassB {
    my $self = shift;
    return $self->{MY_CLASS_B};
}

1;

##</code><code>##

package MyClassB;

use strict;
use warnings 'all';

sub new {
    my $classname = shift;
    my $self = {};
    bless($self, $classname);
    my %extras = @_;
    @$self{keys %extras} = values %extras;
    return $self;
}

sub TO_JSON {
    my $self = shift;
    return { %{$self} };
}

sub getName {
    my $self = shift;
    return $self->{NAME};
}

1;

##</code><code>##

use strict;
use warnings 'all';

use JSON::MaybeXS ':all';
use MyClassA;
use MyClassB;

my $a = MyClassA->new(NAME => 'A instance');
my $b = MyClassB->new(NAME => 'B instance');

$a->setClassB($b);

print JSON->new()->convert_blessed()->encode($a) . "\n";

##</code><code>##

use strict;
use warnings 'all';

use JSON::MaybeXS ':all';
use MyClassA;
use MyClassB;

my $line = <STDIN>;

my $a = bless(JSON->new()->decode($line), 'MyClassA');

print $a->getClassB()->getName() . "\n";