Simple: Perl was most likely being run as CGI. It shows tremendous ignorance to compare Perl running through CGI to Java servlets. Java running through CGI is much slower than Perl. Perl running through mod_perl or FastCGI is just as fast as Java servlets.

It's also possible that the Perl code was awful, written by people who have never heard of CPAN or profiling, but the biggest hit is typically CGI.

Remember, Amazon.com runs large amonts of its site on Perl with FastCGI, and so does Ticketmaster.com (on mod_perl). It's well-established that Perl has good performance.