in reply to Yet another question about cookies.
How the browser stores the cookie is none of your business.
HTTP::Cookies::Microsoft seems to be built to solve a different problem. As I understand, it would be useful if you were writing a Windows web browser in Perl that wanted to read the cookies that were already stored by IE. I don't know why someone would want to that...
However, you seem to be writing a website, so I think CGI::Cookie is the way to go!