OpenBSD pcap_open_offline(3) does not set file descriptor.

Index: t/10-fileno.t
--- t/10-fileno.t.orig
+++ t/10-fileno.t
@@ -111,7 +111,7 @@ SKIP: {
     $fileno = undef;
     eval { $fileno = Net::Pcap::get_selectable_fd($pcap) };
     is( $@, '', "get_selectable_fd() on a dump file" );
-    like( $fileno, '/^\d+$/', " - fileno must be an integer: $fileno" );
+    like( $fileno, '/^(-1|\d+)$/', " - fileno must be an integer: $fileno" );
 }
 
 Net::Pcap::close($pcap);