Speaking as the primary author of a book in one of the popular perl web frameworks (who is having difficulty doing stuff other than perl because a. my skills in perl are too much in demand, and b. Because for most of my normal work I haven't found anything perl can't do as easily or easier than other tools yet) here's my semi-considered opinion.

Meh, all the dynamic languages are basically the same. They're all basically things that manpipulate strings and C pointers. For perl/python/ruby/js here's what I'd sort of recommend:

* Pick from your team's strength, unless:

* Lots of turnkey logic, code quality and debug tools are not a priority, and you want to be able to hire fast and cheap: PHP.

* Lots of turnkey logic, per-performance isn't a problem and you want some higher order programming capability: Ruby.

* You want to manage a java-like large team for not so trivial logic, and you prioritise uniformity over expressivity. Python. Also python is a good environment for academic work as it helps the academic programmers not shoot themselves in the foot so much and academic code is a mess. Which is why python is such a good extension language for other tools.

* Async greenfield stuff where you don't need to worry about external libraries much: javascript. Also the only game in town for web front ends (plus its transpiling friends). Javascript is like a syntatically impoverished perl in this regard.

* You've got a whole bunch of mess in business logic and/or systems logic that you need to encapsulate, and you've got a small highly capable team who want to prioritise expressivity over uniformity. Perl excels here. So does python, but it'll make you do even more horrible things papering over the mess.

Regarding the last point, I believe if it reaches a tipping point perl 6 will be a good thing for async, multicore and parsing related stuff, and should be long-term productive and reduce the requirement for having as highly capable and a disciplined team that is really a requirement for non-trivial perl5 code bases.

Also perl5 is second to none for programming language back compat. I had a decent sized non-trivial project I'd written for internal (research) purposes, then neglected for several years. Then I had to look at the running code again. I'd been through several minor OS upgrades, moved to a completely different OS and gone through at least three major versions of perl. Aside from a couple of missing CPAN modules that I had forgotten about in the Makefile.PL, everything was fine out of the box.