the bottleneck is in general elsewhere, not in your Perl scripts being interpreted, for a web application. It's either the bandwidth (oh, yes...) or the database your Perl script is accessing... While you do take a performance hit it's not something that really affects you. In exchange, with interpreted languages (Perl in particular) you gain access to a level of flexibility that requires a lot more work in other languages. You pay a price you most of the times don't care about because of other factors that influence your performance for development-time flexibility and ease of doing things.

Think about this: A has $10billion in the bank and B has $11billion. Who is richer? Well, A, but really, at this fortune does that $1B really make a difference? They both have more than they need (was about to say "can spend" but I stopped). Similarly, you have other bottlenecks that make your price negligible compared to the benefits (many/most times).