%cookie.foobar% should have worked for you. It did for me.
To log the values of all cookies named foobar, use %cookies.foobar%
To log all cookies, use %cookies%
To log the first cookie, use %cookie%
To log the value of the first cookie, use %cookie.value%
[Message sent by forum member 'jluehe' (jluehe)]
http://forums.java.net/jive/thread.jspa?messageID=255255