Zoopla. It's been a couple of years I left, but I believe they still use Perl for the core business logic. There are wrappers/docker images built on top of them, but Perl is doing all the heavy lifting AFAIK.
IME, big older companies have Perl code chugging along, but not very visible. Part of this is also because there's the perception that it is hard to attract developers if the company mentions Perl any where in the job description.
