If I were doing this with DBIC, it would be as simple as making two connections, and then:

  my $txn= $db2->txn_scope_guard;
  $db2->resultset($table)->populate([
    $db1->resultset($table)->hri->all
  ]);
  $txn->commit;
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assuming you can disable the foreign key checks on the temporary table. If you can't, you'd have to sort the rows so parents come before children, and then that gets more complicated if there is a auto-increment ID column.