I left B.com in early 2020, and they had been using Kubernetes for newer services (I actually worked on the deploy tooling), but until I left nothing of consequence had been moved to containers yet. The overwhelming majority of their workloads still ran on bare metal indeed, and to be really honest I still kinda miss it sometimes.
Booking has competent perl ops people - including people who contribute to the language core and toolchain - and keeps very much up to date.
Sane application scale perl is pretty much a different language to old school scripting perl - the two just happen to share a parser and a VM.
(not everything about Booking's code is necessarily sane, when you've got a codebase that's been running that long making heaps of money there's inevitably stuff people wish they could replace, but your 'most likely' simply isn't descriptive of most companies running OO perl application stacks in 2022 - the ones that wrote crap perl mostly already blamed perl and are now writing hopefully slightly less crap something else)
Their code base is (still) mostly in Perl (5), running on uWSGI bare instances, installed on KVMs deployed on a self-hosted infrastructure.