Hi,
as said, install the two modules mentined above. Then do
perl -MWWW::Mechanize::Shell -eshell
You will end up in that shell. Type help for help, then e.g. type connect http://bla.bla to connect to that URL.
Make your way through the pages (it's a bit like using a text browser). Remember: help is at hand
When you have what you wanted to do, type
script myscript
After quitting the shell (the Mechanize-Shell), you find a file called myscript in your directory that contains the code that will do exactly what you did in the shell.
This page should help you.
update: passing Apache Basic Auth. creditial with WWW::Mechanize? has some information on the auth part of your problem
Regards,
svenXY