hmm ... I think you should rather think in terms of programming paradigms to broaden your horizon than "fun languages".

Fun languages are a matter of fashion and hypes, but paradigms prevail.

Perl is a multi paradigm language, which I enjoy a lot (and frustrates others)

Larry created a kind of "Frankenstein's Monster" (tongue in cheek) by sewing together elements of C, bash, awk, sed and Lisp, among others, this led to quick success because ppl coming from those languages quickly felt comfortable.

You can try using Perl from these different angles to approach other languages.

For Functional programming: Higher Order Perl comes to mind. From there you can have a look at LISP (or Scheme to be more specific)

If you don't like Lisp's syntax, you might wanna have a look at Haskell.

Of course there are more languages which are outside the paradigms covered by Perl, like Forth, Erlang or Prolog.

edit

The book Seven languages in seven weeks may also be of interest for you, tho I would switch Io with JS.

update

The books covers most of what I've already mentioned, here my 2022 take on them

• Ruby:

  basically a redesign of Perl ideas with a powerful standard OO system, but included out-of-the box. Plus a sexy syntax, facilitating the design of DSLs, (IMHO Perl6 should have taken this direction, but without breaking backwards compatibility)

• Io:

  The unknown sister of JS in using prototype based OO.

• Prolog:

  List processing, classic approach to AI. There are CPAN modules for doing this inside Perl

• Scala:

  use the JVM with a lot of DWIM. Resource heavy in production, really bad for global warming. (This niche is targeted by Kotlin nowadays with much less processor heating - hype alert :)

• Erlang:

  High Availability for TelCos

• Clojure:

  Lisp for the JVM, better readable syntax tho

• Haskell:

  the dream of computer scientists, but maybe too intelligent for the rest. (The volume of the WWW nearly doubled with blogs trying to explain what a Monad is ;)

update

DISCLAIMER: I'm not proficient in most mentioned languages, my short characterizations are far from being complete.