I'm as confused as corion. (Note to corion: I think that "control IDs" as referred to by OP are talking about HTML id attributes, plus the possible class attributes).

If you want to programmatically retrieve a web page from a server using Perl instead of using a web browser at all, you can use LWP::UserAgent. That gives your Perl code the ability to retrieve HTML pages, even if there are cookie and/or authentication requirements. You then can have access to the HTML source of the page and can parse it using HTML::Tree or perhaps and get the ids and classes. Note that if the goal is to simply provide a list of ids/classes/elements in a page, you do NOT want to start down the path of using regular expressions to parse the HTML.

But, most importantly of all, you have to specify what you are trying to do (and not just "get the IDs and classes"). If you tell us what real world problem you're trying to solve, then you will get much more specific recommendations