Booking.com is a big place where newbies will be sitting with lots of experienced people they can ask and discuss with over lunch/coffee.

I doubt that smaller places will see so fast ramp up that they don't bother to hire people that know the language environment. The language in itself is quite irrelevant, but building a taste and learning the standard libs (here -- CPAN) takes time. That goes for every environment.

Edit: It would be interesting to hear the experience on this at other big shops? Maybe material for an academic article, someone?

Edit 2: I might add -- the differences between the scripting languages seems a bit overblown in the article. The languages (Perl, Ruby et al) aren't that different. Here I argued about the environment and standard libraries, which takes many, many hours for at least Python and Perl. And for taste -- to not have anonymous functions in Python needs changes in how you code. And so on.