While this might be just as confusing as things you've seen or tried, it's minimal and available: CGI/Ajax example: lookup a value when a field is filled in.
The main problem with web development isn't that any part of it is hard, it's not, it's that there are so many moving parts. Writing dynamic forms / ajax stuff + the backend is not a beginner task, even for someone seasoned in other programming. You might be feeling lost and like Perl is a wasteland but I assure you it's one of the best for web work; as is jQuery. If you post code you are working on, you'll probably get good help.
One thing you said leads me to believe you are using CGI and doing this kind of thing-
print "Content-Type: text/html\r\n\r\n",
There are many ways to get output out in Perl. The CGI.pm proper module is quite old-school. It's not a first choice for production but sometimes can be for one-offs and learning as long as you're aware better (more robust, testable, and reusable) approaches exist. Still, it's serviceable and stronger than most give it credit. You can, e.g., one page, one print-
use CGI ":standard";
p([ "one", "two", "three" ]),