Perl vs PHP speed?

We expect about 570 new visitors every minute on our web page
containing a form, 17 of these will press a submit button to invoke the
PHP (alternatively CGI perl).

Would you expect the performance hit to noticeable at this volume, thus
we should consider a cgi-bin perl instead of PHP (parser is loaded).
Perl is after all never invoked unless submit is pressed.

We would also like to store the referrer in a cookie when someone
enters the page, this could be done with PHP. Maybe javascript is
quicker (avoiding PHP parser)?