Is there such utility functions in Perl?

1. Get current requested url (no parameters)
2. Get all GET parameters as hash
3. Convert hash to key1=val1&key2=val2...

I think these are necessary tools in web development.

How do you do this in Perl?

It sounds like you're trying to re-invent web development again from scratch. Don't do this.

The CGI module is also probably not a good place to start if you're new to this. Look at one of the many modern frameworks that already exist to prevent you from having to ever care about parsing request parameters, construct GET URL's and the like.

I like Mojolicious but it's one of many.

The CGI module provides all of these functions.