I'm working in Ruby, but my question is valid for other languages as well.
I have a Mechanize-driven application. The server I'm talking to sets a cookie using JavaScript (rather than standard set-cookie), so Mechanize doesn't catch the cookie. I need to pass that cookie back on the next GET request.
The good news is that I already know the value of the cookie, but I don't know how to tell Mechanize to include it in my next GET request.
These answers are old, so to bring this up to date, these days it looks more like this:
cookie = Mechanize::Cookie.new :domain => '.mydomain.com', :name => name, :value => value, :path => '/', :expires => (Date.today + 1).to_s
agent.cookie_jar << cookie