Slashdot gets a lot of hits and runs perl. <...> In the end it all comes down to good design and network architectures.
Doesn't Slashdot have a big fat load balancing system in place? The speed issue was dealt with by throwing more hardware at the problem. So, like you said, it comes down to design and achitecture. I suppose somebody could code a website using Q-BASIC on several heavy duty machines behind a load balancing system, but that's probably not good design.
To me, I find Perl very fast and easy to develop with. Not only is CPAN sweet, but PerlDoc rocks as well. I use references constantly when I code, and PerlDoc is always there when I need a hint.