Even today, Perl is the only scripting language with more than 200K modules and no Global Interpreter Lock.
The "interpreter-based threads" provided by Perl are not the fast, lightweight system for multitasking that one might expect or hope for. Threads are implemented in a way that makes them easy to misuse. Few people know how to use them correctly or will be able to provide help.
As a result, threaded Perl code or frameworks are extremely uncommon, even relative to Python.