iRule Cookie Rewrite Domain w/ Subdomain

Hi all,

We have a requirement whereby we need to ensure that a sub-domain on a cookie domain persists all the way to one of our back-end Oracle servers (Oracle requires a sub-domain). The cookie is written to the browser with the domain "qa-my.bar.com", however on the requests set to the back-end server, I need to ensure that the domain is "qa-foo.bar.com". It seems that you can't do this in an iRule because setting the domain property of the cookie to "qa-foo.bar.com" fails because the iRule won't let you set the sub-domain - setting the domain to ".bar.com" works.

Is this even possible? If so, any recommendations on how to do this?