Why is Perl so afraid of "deep recursion"?

Question

I recently stumbled across the book Higher-order Perl, which basically suggests ways to do things in Perl in a functional way. The author explains that Perl has 6 out of 7 core features of Lisp, while C has none.

I had a problem which looked like a good candidate for a recursive solution, and I coded it in this fashion. But Perl complained about "deep recursion". I googled a bit and found a Perl monk explaining that "Perl is not Haskell". Apperently you get a complaint by default, when the recursion depth exceeds 100 levels.

There are ways to extend this limit or to turn it off entirely, but my question is:

• Is there a reason that Perl is so uptight about recursion, while Haskell is not at all?

Answer 1

Because in Haskell, we have laziness & guarded recursion and tail call optimization and Perl has neither.

This essentially means that every function call allocates a set amount of memory called "the stack" until the function returns. When you write recursive code, you build up a huge amount of memory because of these nested function calls and eventually can stack overflow. TCO allows the unused chunks to be optimized away.

Without this it's not really a good idea to rely on recursion. For example, say you wrote a recursive version of map, it'd crash with any decent sized list. In Haskell, guarded recursion means that with large lists, the recursive solution is much faster than a "loop" like function.

TLDR: Haskell's implementations are designed to handle a functional/recursive style and perl's implementation is not and back in the good old days, 100 levels of function calls was a sane limit.