What is the best, most versatile, most acceptable way to get the data submitted from a web form into my perl script?

Multiple times I have posted some code along with my questions here at PerlMonks, and multiple times I have been told to use CGI.pm to get the form data rather than what I had in my code. However, I have not yet been told how to do so, nor have I been able to find the correct way I should do so.

Could someone please provide a good, solid sample (or multiple variants) of exactly how to get the data from a form to a hash variable in a perl script. I am looking for an example with separate HTML page and Perl script code, however, Perl only code examples may also be provided.