You get simply a big chunk of data with the entire result of the HTTP request. I usually load it to a variable. Then you can process it any way you want, even grep it for strings. Note that if the HTML has references to other items such as images you'll have to load them by yourself.

Curl does process POST's and GET's very well.

If you use perl with WWW::Curl, I suggest you use HTML::Parser and/or HTML::TokeParser. It's easy to use to interpret the HTML file. For python it seems there is python-html5lib.

Note also that you have the option of using WWW::Mechanize in perl and python-mehanize, but I have no experience with this.