The now defunct Perl Month, ran a feature some time ago benchmarking mod_perl, perl cgi, php4, asp, java servlets, and a few perl based templating systems. The article is a bit dated but you can find the article here.

I recently ported a fairly elaborate web based quiz application from PHP to perl and I haven't noticed any significant speed difference between the PHP and perl versions. Keep in mind that your biggest bottleneck will most likely be network related.

Given the choice between perl and PHP, I would definately go with perl. The perl version of my application turned out much cleaner than the PHP version primarily due to CPAN, DBI, the Template Toolkit and use strict. PHP still seems a bit rough around the edges to me.

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Coyote