Taint mode blocks vulnerability

If filename is `ARG`, the while loop will call `open()` on every thing in `@ARG` creating a remote execution vulnerability. Enabling taint mode prevents this. See my [article](http://perltricks.com/article/netanel-rubins-perljam-circus/http://perltricks.com/article/netanel-rubins-perljam-circus/) for details.
Another way to fix would be to use the double diamond operator `<<$file>>` will not call `open()`. But it requires Perl 5.22.0 or higher, which most people won't have.

examples/file_upload.cgi

@@ -1,4 +1,4 @@
-#!/usr/bin/env perl
+#!/usr/bin/env perl -T
 
 use strict;
 use warnings;