For example, you can undef the model, but its destructor isn't called, as it's still referenced from the tables:

#!/usr/bin/perl
use warnings;
use strict;

{
    package Myproject::Model::Table;
    use Moo;
    has name => (is => 'ro');
    has model => (is => 'ro');
}

{
    package Myproject::Model;
    use Moo;

    has table => (is => 'rw');

    sub newtable {
        my ($self, $name) = @_;
        my $tob = 'Myproject::Model::Table'->new(
            name => $name,
            model => $self,
        );
        $self->table or $self->table({});
        $self->table->{$name} = $tob;
    }
    sub DESTROY { print "Good bye\n"; }
}

my $model = 'Myproject::Model'->new;
$model->newtable('t1');
undef $model; # No destructor called here.

use Data::Dumper;
print Dumper $model;
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To get the destructor called, you can modify the definition of the model attribute like this:

    has model => (is => 'ro', weak_ref => 1);
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($q=q:Sq=~/;[c](.)(.)/;chr(-||-|5+lengthSq)`"S|oS2"`map{chr |+ord
}map{substrSq`S_+|`|}3E|-|`7**2-3:)=~y+S|`+$1,++print+eval$q,q,a,
[download]