I also hear Blekko is all Perl (it's the dmoz directory-people making a search engine. it's got social-search-related features, too, or something like that.) Apparently they have some fancy sophisticated technology for their backend systems (store big bitfield indexes on SSDs with a disk-backed store for the rest, spread across dozens of nodes, etc.) But I don't know anyone actually working there.
If you have the initiative you can look up their job applications yourself :P