Inside Object2:
   sub setsomething {
      my $self = shift;
      $self->{_object1}->{mode} = 1;
   }

##</code><code>##

sub mode
{
  my $self = shift;
  $self->{mode} = $_[0] if (@_);
  $self->{mode};
}

##</code><code>##

$self->{_object1}->{mode} = 1;

##</code><code>##

$self->{_object1}->mode(1);