multiple URI redirects

My 9.x coding is a little rusty, but I think it'd go something like this:

Data group (example: "my_datagroup")

"/parentdirectory1/ hostname1"
"/parentdirectory2/ hostname2"
...
"/parentdirectory300/ hostname300" 

iRule

when HTTP_REQUEST {
    if { ( [string tolower [HTTP::host]] equals "hostname.com" ) and ( [matchclass [string tolower [HTTP::uri]] starts_with my_datagroup] ) } {
        set newhost [findclass [string tolower [HTTP::uri]] my_datagroup " "]
        HTTP::redirect "http://$newhost[HTTP::uri]"
    }
}