I think Perl lost to Ruby because of Rails. Whilst Perl had a couple of web frameworks - Catalyst, Mojolicious and Dancer - they never gained anywhere near the traction of Rails. I think this was because Perl's early success in the 90s was based on CGI.pm, not frameworks. Catalyst gained a little adoption at a few big companies but it was hobbled by dependence on mod_perl which had a much riskier memory mode for hosting companies than mod_php. Perl was also a bit late shedding its mod_perl legacy by which time Ruby had Rack and Python had WSGI. Despite the brilliant work of Miyagawa it was game over by the time PSGI and Plack appeared.