Redirect from bare domain to www site in VCL3

bareDomainRedirectVCL3.vcl

sub vcl_recv {
  if (req.http.host !~ "www") {
    error 850 "Moved Permanently";
  }
}

sub vcl_error {
  if(obj.status == 850) {
    set obj.http.Location = "https://www." + req.http.host + req.url;
    set obj.status = 301;
    return(deliver);
  }
}