Is debugging functional oriented code harder?

Hi,

in popular languages like Perl, Python or C it's easy to add debug mechanisms into existing code, increasing it or decreasing their verbosity and details, it's also easy to add prints, that indicate execution flow of process.

How is it functional languages, where you can't just insert them? I tried this approach when I started to learn Haskell and results were miserable. Also some of you may say, that real world programmer should prefer debuggers, but I think, it's just different tool, they are usable, but for some cases prints or logs are much better. My questions are, do you use logging mechanism in your functional languages? Do you use somehow ordinal prints for this? Are there better ways?

Debugging functional _^Lisp code is easier, I just open up the REPL, load the code, call the function with some test parameters, check if it's correct. Don't know for Haskell, but it should be more or less the same.