Perl's decline relative to PHP is a bit more nuanced. With mod_perl you had to be really careful with global variables otherwise another process could access t

Perl's decline relative to PHP is a bit more nuanced. With mod_perl you had to be really careful with global variables otherwise another process could access them in memory. Mod_php did a better job of isolating processes so mod_perl gained a reputation as a security headache which most cheap hosting companies were not prepared to deal with. It's often overlooked that a lot of cheap hosts only offer PHP as a CGI so the benefits over Perl/CGI appear, at first glance, to be minimal but even as a CGI PHP has templating built-in where Perl, Python and Ruby don't. Perl only has CGI.pm when limited to CGI. Sure, you can try to run Perl web frameworks such a Mojolicious, Dancer and Catalyst under CGI but they're not going to compete with PHP since they don't run as drop-in templated pages. Perl did have a PHP clone - HTML::Mason - but it wasn't worth using unless you ran it with mod_perl. That's where Perl lost to PHP. When PHP gained full OOP support with PHP5 the Perl community was still tearing itself apart over introducing a MOP and which of the dozen Moose clones should reign supreme. That was the final nail in Perl's coffin, at least in it's bid to compete with PHP.