iRule Assistance with redirecting multiple URLs to a single URL using an existing Redirect iRule

Assuming you want to keep , the following additional entry should cover the four examples you listed:

when HTTP_REQUEST {
   switch -glob [string tolower [HTTP::host]] {   
      "*www.sitename.net*" {
         HTTP::redirect "https://sitename.sitename.com"
      }
      "*sitename.com" {
         HTTP::redirect "https://www.sitename.io"
      }
      default {
          add the default action you prefer ie "www.def.com"
         HTTP::redirect "https://[HTTP::host][HTTP::uri]"
      }
   }
}