What larger companies use Perl for their underlying architecture?

We're not "large" if you look at number of employees, but craigslist is about 95% Perl internally.

I just got hired by Opera Software for a Perl programming position :)

Riverbed's QA uses Pe...

Leading B2B portal in India: http://www.indiamart.com is using mod_perl

Amazon started out as a Perl shop, and is mostly still Perl. The BBC is almost entirely a Perl shop, as is IMDb.

http://Mail.Ru Group, the biggest russian internet company has a lot of Perl inside its main assets (web mail, social network). MRG is also the biggest publicly traded internet company in Europe. Other big russian companies like Yandex and Rambler also rely on Perl code heavily both for new and old projects.

http://booking.com is known to be a Perl shop. Constantly looking for new talent. And my employer .SE the Swedish ccTLD registry is a Perl shop as well.

In Southern California we have Ticketmaster, http://Oversee.net, http://Rent.com, ValueClick, Shopzilla, PriceGrabber, Rubicon, MediaTemple, and Yahoo (ex-Overture) just that I know of personally.  We have lots of smaller shops too, of course.

Blekko is Perl and XS; I believe DuckDuckGo is Perl as well. I can add (now that I work there) WhiteHat Security to that list (though we're quite promiscuous: I've done stuff in Python, Java and Mono there as well), and an awful lot of infrastructure is done in Perl at Yahoo!.