my $authorityserverdir = C4::Context->zebraconfig('authorityserver')->{directory};
my $kohadir = C4::Context->config('intranetdir');
-my $bib_index_mode = C4::Context->config('zebra_bib_index_mode') || 'grs1';
-my $auth_index_mode = C4::Context->config('zebra_auth_index_mode') || 'dom';
+my $bib_index_mode = C4::Context->config('zebra_bib_index_mode') // 'dom';
+my $auth_index_mode = C4::Context->config('zebra_auth_index_mode') // 'dom';
my $dbh = C4::Context->dbh;
my ($biblionumbertagfield,$biblionumbertagsubfield) = &GetMarcFromKohaField("biblio.biblionumber","");