The largest reason why I would hesitate to use Perl in my startup would be the core philosophy of TIMTOWTDI (there is more than one way to do it). Being able to write something multiple different ways leads to Perl being a lot easier to write than it is to read. As a result code maintenance can become a huge headache due to someone not understanding the idioms used by the person who originally wrote the code.

I've seen this happen on a number of projects that I've worked with using Perl. Typically a person wouldn't be familiar with "silver ball" (Effective Perl Programming), would go off an write a large body of code which would be difficult to wade through. This gets exacerbated by new coders not understanding how perl expects you to understand some of its idioms (like $_, @_, etc.) implicitly. Because reading other people's code is a great way to learn a language, this makes Perl a lot less approachable.

I think Ruby suffers from some of these problems to a certain degree as well. I haven't worked with Ruby professionally, but in the few times I've played around with it I've found myself spending a lot of time trying to figure out which looping construct I should use over another.

Python does have a leg up in this department. The language tends to be fairly succinct and things like Pep8 and flake8 really help in making most code fairly digestible.