use strict;
use warnings;
use Devel::Cycle;

package A;
use Scalar::Util qw/weaken/;
sub new {
    my ( $class, $href ) = @_;
    my $self = { dbi => $$href{dbi} };
    my $weak_self = $self;
    weaken $weak_self;
    $self->{helper} =
        Helper->new( helper_function => sub { $weak_self->this_is_from_A(@_) } );
    bless $self, $class;
}
# ....the rest remains unchanged.