Cookies are a browser thing really, there is no standard how to implement them. It's even more vage for javascript cookies.

For debugging, check if you cookie is visible to javascript (a reload after you set it):

alert(document.cookie);
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In your script, check if the cookie is available in the environment:

print $ENV{'HTTP_COOKIE'};
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If the last example does display the cookie, something might be wrong with CGI.pm. An old version maybe?