update: Oops! I posted this, clearly, in the wrong thread. I intended to post it in the thread about which other languages are good to learn along with Perl. Sorry for any confusion.
My first suggestion would be lisp. It's a very nice
language, similar enough to Perl that if you like one
you may like the other, but different enough from Perl
to stretch the way you think about programming just
a little. Lisp, like Perl, is a general-purpose
programming language.
Another possibility is Inform. Inform is not a
general-purpose language, but is targeted toward a
fairly narrow (but very interesting) problem domain.
It's Turing equivalent, of course, and quite flexible,
but really geared toward a specific type of program.
The advantages of Inform are twofold. First, it
will teach you to really appreciate the object-oriented
paradigm, because the object model in Inform is pretty
advanced (WAY beyond the Perl5 one), and a *very* good
fit for the intended problem domain. Second, Inform
has a really excellent book, the Designer's Manual,
which is without qualification the best computer-related
book I have ever seen. (It's also available online
(free of charge), as well as in print.) Inform will
change the way you think about object-oriented
programming, guaranteed. Oh, and the intended
problem domain is one that immediately captures
the imagination, so it's fun to program in.
