My hunch is that it's pretty rare to see a new startup using Perl, Erlang, C++ or even Java.

It depends a lot on the business and the sector. Serious startups in fields like biotech, nanotech and finance are still very commonly using languages like C, C++, Java and F# for new projects.

These are companies creating software that'll likely still be around and in use 10 or 20 years from now, rather than web startups who will likely not survive more than a couple of years, or will rewrite their software time and time again using whatever the current over-hyped language/platform of the day is.

Also they don't get the attention the hot languages get.

However there are some Perl startups, for eg: Lokku, Blekko, Moonfruit, DuckDuckGo, CareerJet & Adzuna

This is one: http://news.ycombinator.com/item?id=4461427