PHP was always one of the top ecosystem for web development (probably the top one in the early 2000s), with strong platforms and userbases centered around them: LAMP, wordpress, discussion boards and other.
Perl never had anything like that. It allowed to do CGI in the early 1990s then nothing major I can think of.
Depends what you mean by widely-used. After Rails and Django appeared I can't remember many high-profile sites using any of the Perl frameworks. Maybe Catalyst at the BBC and Net-A-Porter who hired a lot of Perl gurus. Perl's realy failure was competing with PHP. Perl's equivalent, HTML::Mason, really required mod_perl to perform anywhere near mod_php and that's what killed it as mod_perl was not an option for cheap hosting providers. PHP was as much a marketing coup as anything else, hence Facebook built on PHP. I think it says everything that Dustin Moskovitz mistakenly picked-up a Perl textbook before he was corrected by Mark Zuckerberg that they were using PHP. That's exactly where Perl stood in relation to PHP in early 2004.
Yes, that's how I remember it. It's also worth noting that the fun parts of perl were largely replaced by ruby. The ruby one-liners and perl one-liners are pretty much the same. And eventually, gems got bigger than CPAN.
You're also right about mod_perl vs php. Shared hosting was really common and mod_perl was really unpleasant.
At some point it's just goodbye perl and thanks for all the scripts.
Yes, there was real apathy in the Perl community - an attitude that Perl is a better language than PHP so why should we lower ourselves to compete. The endless MOP debates didn't help either and for those waiting for Perl to sort it out Ruby was there with everything they needed. Moose, Moo, Mouse - talk about fiddling while Rome burns. Perl was in no state to compete with Rails' elegantly-packaged Omakase. Another factor which affected Perl 5 in the mid-2000s was the diversion of resources to Perl 6 when Perl 5 had 3 sharks (PHP, Ruby & Python) circling around it. Meanwhile newsagents' shelves were full of dedicated PHP & MySQL magazines and the more generic web dev mags invariably had an advanced section featuring sites buillt with PHP & MySQL. It was already game over for Perl.
Perl never had anything like that. It allowed to do CGI in the early 1990s then nothing major I can think of.