A big contributor to the demise of Perl, IMHO, was the failure of Catalyst and mod_perl to compete with PHP and Rails. mod_perl security was too risky for most ISPs and Catalyst, with it's clunky subroutine attributes style of routing and hefty CPAN dependencies, was a pain to get up and running. Mojolicious was a big improvement but too late to stop the PHP and Rails defections.