Also, I think you want an if, not a while

No, that's how you're supposed to use CGI::Fast, as a glance into the documentation would have told you. The whole point of FCGI is a persistent process.

strict/warnings would not have caught the infinite loop tho

It would?

(Somehow I missed the "not" in that sentence, my apologies.)

Maybe nodes{ exists $nodes{$query} ? $query : '_err' }(); needs to be nodes{ exists $nodes{$query} ? $query : '_err' }->();

No.

hippo's answer is correct: The problem is there are two CGI objects in the program.