Yuval Kogman came up with a KiokuDB solution:

#!/usr/bin/perl -w

use strict;
use warnings;

use Time::HiRes qw(sleep);
use Test::More 'no_plan';

{

    package Simple;
    use Moose;

    has 'nums' => (
        isa     => 'ArrayRef[Int]',
        is      => 'rw',
        default => sub { [] },
    );

}

use KiokuDB;
use Parallel::ForkManager;

my @in = 1 .. 50;
our @out;

my $pm = new Parallel::ForkManager(5);

my $dir = KiokuDB->connect( "dbi:SQLite:dbname=kiokudb_tutorial.db", c
+reate => 1 );

my ( $id ) = $dir->txn_do( scope => 1, body => sub { $dir->insert( Sim
+ple->new ) } );

warn "id: $id";

for my $link (@in) {
    $pm->start and next;

    retry: {
        eval {
            $dir->txn_do(
                scope => 1,
                body  => sub {
                    my $obj = $dir->lookup($id);

                    push @{ $obj->nums }, $link;

                    $dir->update($obj);
                }
            );
        };

        if ( $@ ) {
            warn "$$ failed to commit, sleeping for random interval an
+d retrying";
            my $i = rand(0.1);
            sleep $i;
            redo retry;
        } else {
            warn "$$ successfully comitted";
        }
    };

    $pm->finish;

}

$pm->wait_all_children;

$dir->txn_do( scope => 1, body => sub {
    my $obj = $dir->lookup($id);
    
    is( scalar(@{ $obj->nums }), scalar(@in), "update count is correct
+" );

    warn $obj->dump;
});
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