Well, true, but <nit>
We're untainting only to the extent that we're performing a function that Perl (uncritically) reads as untainting... but without any substantive untainting...

In other words, <c>(($this_mail) = ($this_in =~ /(.*)/gio));<c> passes the entire tainted input without any attempt to cull out unacceptable content.

</nit> (or is it merely a nit?)