TCL errors

The syntax for a class match -value is:

class match -value

This means "retrieve the value associated with the key in the data group named ". In your case, the Host header is "google", so in your code, once HTTP::host expands, you are trying to do this:

class match -value [HTTP::uri] equals VURL_google

but there is no data group named "VURL_google". I suspect you're confusing the use of equals here, which is actually a parameter of class, rather than the normal equals operator. I believe you are trying to lookup the value in a data group that is associated with the key HTTP::uri, then see if that value matches the literal "VURL_google". If I'm right, then let's assume your URI->host matching data group is called dg-uri-host. Your code would be:

when HTTP_REQUEST {
    set redirect_url [class lookup [string tolower [HTTP::uri]] dg-uri-host]
    HTTP::redirect $redirect_url
}

If you were trying to make this conditional, then it would be:

when HTTP_REQUEST {
    set redirect_url [class lookup [string tolower [HTTP::uri]] dg-uri-host]

    if { $redirect_url eq "VURL_google" } {
        HTTP::redirect $redirect_url
    }
}

Note that this:

class lookup

is synonymous with this:

class match -value equals

Also note that HTTP::uri is the entire query-uri, which means that, if a client submitted this:

GET /foo/bar/baz.html?this=that&here=there

then HTTP::uri would be "/foo/bar/baz.html?this=that&here=there". You might find the use of HTTP::path more fruitful. Also, while your filesystem may or may not be case-sensitive, the Request-URI path is in fact case-sensitive, so normalizing the case (that is, using string tolower) on the Request-URI or Request-URI path is -- strictly speaking -- not needed and in fact causes differing paths to appear to be equal.