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

package A;

sub new {
	my ($class, $href) = @_;
	my $self = { dbi => $$href{dbi} };
	$self->{helper_child} = Helper->new(
		parent => $self,
		helper_function => sub {
			my $parent = shift;
			$parent->this_is_in_A(@_);
		}, );
	bless $self, $class;
}

sub do_something {
	my $self = shift;
	$self->{helper_child}->do_helper();
}

sub this_is_in_A {
	my ($self, $arg) = @_;
	print "this_is_in_A, arg: $arg, dbi is $self->{dbi}\n";
}

sub DESTROY { print shift."->DESTROY\n" }

package Helper;
use Scalar::Util qw/weaken/;

sub new {
	my $class = shift;
	my $self = { @_ };
	weaken( $self->{parent} );
	bless $self, $class;
}

sub do_helper {
	my $self = shift;
	$self->{helper_function}->($self->{parent}, "param from Helper");
}

sub DESTROY { print shift."->DESTROY\n" }

package main;
my $x = A->new( { dbi => "some dbi object" } );
$x->do_something();
$x->do_something();

find_cycle($x);

print "undef'ing \$x\n";
$x = undef;
print "End\n";

__END__

this_is_in_A, arg: param from Helper, dbi is some dbi object
this_is_in_A, arg: param from Helper, dbi is some dbi object
undef'ing $x
A=HASH(0x55e36742fc88)->DESTROY
Helper=HASH(0x55e36742fdc0)->DESTROY
End