+my $biblionumber = $query->param('biblionumber');
+my $record = GetMarcBiblio($biblionumber);
+
+if ( not defined $record ) {
+ # biblionumber invalid -> report and exit
+ $template->param( unknownbiblionumber => 1,
+ biblionumber => $biblionumber );
+ output_html_with_http_headers $query, $cookie, $template->output;
+ exit;
+}
+