...
             my $duplicates;
             my $old_target = $target;
             while( $filenames{ $target }) {
                 $duplicates++;
                 ( $target = $old_target )=~ s!\.(\w+)$!_$duplicates.$1!;
             };
-            $names->{ $res->{url} } = $target;
+            $names->{ $res->{url} } = File::Spec->catfile( $base_dir, $target );
         };