Have you read WWW::Mechanize::Firefox and HTTP::Cookies::MozRepl?

What makes you think that HTTP::Cookies would work together with WWW::Mechanize::Firefox and/or that WWW::Mechanize::Firefox would use a cookie jar outside of Firefox?

Thanks for your response, Corion. It was silly of me to presume.
I tried the following code with Mechanize::Firefox and won't work to save cookies:

my $cookie_jar = HTTP::Cookies::MozRepl->new( file => 'C:\path\to\cook
+ies.dat', autosave => 1, ignore_discard => 1);
[download]

Where did you find these parameters documented in HTTP::Cookies::MozRepl?