Your MyClass constructor is all wrong:

sub new {
    my $self = {};
    
    $self->{ObjA_ref} = shift; ## This is the class name Eg. 'MyClass'
    $self->{ObjB_ref} = shift; ## This is the ClassA ref


    bless $self;
    return $self;
}
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Try something like this:

    sub new {
        my $class = shift; ##NB
        my $self = {};

        $self->{ObjA_ref} = shift;
        $self->{ObjB_ref} = shift;


        bless $self, $class;
        return $self;
    }
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