I'm going to make a broad generalization and guess that your boss wants you to do it in PHP because "nobody uses Perl for websites anymore". If that is indeed his objection you might point out that amazon.com, slashdot.org and about.com all run on Perl (amazon and about use Mason). As far as a direct comparison you would do better to compare one of the Perl frameworks vs. PHP rather than Perl itself. I don't know how much web programming experience you have or if you have a preffered way of developing web technology in Perl, but I think you would get more milage out of comparing Perl/Mason or Perl/HTML::Template vs. PHP.