$pfm->run_on_finish (
      sub {

        my ($pid, $exit_code, $ident, $exit_signal, $core_dump,
          $data_structure_reference) = @_;
        if ( defined $data_structure_reference ) {

          my $delete_list = $data_structure_reference->{delete_list};
          my $insert_list = $data_structure_reference->{insert_list};