#!/usr/bin/env perl

use FindBin '$Bin';
use lib "$Bin/local/lib/perl5", "$Bin/lib";
use v5.16;
use warnings;

use My::Schema;

use Data::Dumper;

my $schema = My::Schema->my_connect;

my $COSTS = $schema->resultset('Cost');

sub create {
    my ($amount) = @_;
    $amount //= 0;

    $COSTS->create({
        resource_id => 1,
        amount => $amount,
        currency => 'EUR',
        recurrence => 'monthly',
        comment => 'hi',
    });
}

eval {
    $schema->txn_do(sub {
        say 'creating record 1';
        create(1);
        say 'created rec 1';
        say 'disconnecting';
        $schema->storage->dbh->disconnect;
        say 'creating record 2';
        create(2);
        say 'created rec 2';
    });
};

if (my $e = $@) {
    say 'caught error';
    say Dumper($e);
}

say 'creating rec 3';
create(3);

__END__

Output follows:

creating record 1
created rec 1
disconnecting
creating record 2
creating record 1
created rec 1
disconnecting
creating record 2
caught error
$VAR1 = bless( {
                 'msg' => '{UNKNOWN}: Transaction aborted: DBIx::Class::Storage::DBI::_dbh_execute(): DBI Exception: DBD::mysql::st execute failed: MySQL server has gone away [for Statement "INSERT INTO cost ( amount, comment, currency, recurrence, resource_id) VALUES ( ?, ?, ?, ?, ? )" with ParamValues: 0=2, 1=\'hi\', 2=\'EUR\', 3=\'monthly\', 4=1] at ./test.pl line 20
. Rollback failed: lost connection to storage at ./test.pl line 39
'
               }, 'DBIx::Class::Exception' );

creating rec 3
DBIx::Class::Storage::DBI::_dbh_execute(): DBI Exception: DBD::mysql::st execute failed: MySQL server has gone away [for Statement "INSERT INTO cost ( amount, comment, currency, recurrence, resource_id) VALUES ( ?, ?, ?, ?, ? )" with ParamValues: 0=3, 1='hi', 2='EUR', 3='monthly', 4=1] at ./test.pl line 20


...and absolutely no records were created in the table.