$self->_send_summary_email(
[ map { $_->{invoice} } @new_invoices ],
[ map { $_->{invoice} } @invoices_to_print ],
[ map { $_->{invoice} } @invoices_to_email ],
$self->_send_summary_email(
[ map { $_->{invoice} } @new_invoices ],
[ map { $_->{invoice} } @invoices_to_print ],
[ map { $_->{invoice} } @invoices_to_email ],