Applications from well-known companies that I've worked on:

• Motorola uses Perl to test upgrades to their cellular network infrastructure. (My code was used at Ground-Zero to look for cell signals.)
• MasterCard uses Perl/Apache/MySQL to power one of their most visible web applications for corporate customers.
• BankOne uses Perl to load all its Stock and Bond processing. (Over 5_000_000 records per night)

Most web companies use Perl. They may not admit it, but they do.