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?

>>2
>>3
You're right, but it's a good way when you create code, but what when you do  maintenance? What if you have complicated scenario, when you don't know when or why it fails? Testing single functions is hopeless in those cases, but some module tests + good debugs can made the job.