Converting Regex to iRule

Thanks Aaron, however that seem to change anything. I'm still being redirected to my production website instead of the content mangement interface of the test site, and I've only have this applied to my test site, which makes it even stanger.

I'm attempting to add in some logging so I can confirm that its at least seeing it, and maybe try to figure out when its applying the rule, however i'm doing something wrong because its saying wrong agr for header, any thoughts on what I'm missing here:

when HTTP_REQUEST {
    switch "[string tolower [HTTP::host]]" {
        "test.sitename.us.com" -
        "cms.test.sitename.us.com" {
log local0. before:[HTTP::header]
            HTTP::header replace Host "sitename.us.com"
log local0. after:[HTTP::header]
        }
    }
}

Thanks,

Bob