Varnish: vcl_error redirection

Question

I have a few question about Varnish configuration. I've got this simple config file:

backend default {
  .host = "127.0.0.1";
  .port = "80";
}

sub vcl_recv {

if (req.http.Host == "192.168.1.100")
  {
    set req.http.Location = "http://example.com" req.url;
    error 750 "Permanently moved - TEST";
  }
}

sub vcl_error {

if (obj.status == 750) {
  set obj.http.Location = req.http.Location;
  set obj.status = 301;
  return(deliver);
 }
}

Question:

(1) I've followed this example: set req.http.Location = "http://example.com" + req.url; - however I'm not able to reload Varnish unless I remove this + symbol - is it required and what's the purpose of it?

# /etc/init.d/varnish reload
Loading vcl from /etc/varnish/default.vcl
Current running config name is reload_2013-12-17T15:01:43
Using new config name reload_2013-12-17T15:18:31
Message from VCC-compiler:
Expected variable, string or semicolon
(input Line 124 Pos 58)
    set req.http.Location = "http://example.com" + req.url;
---------------------------------------------------------#---------
Running VCC-compiler failed, exit 1VCL compilation failed
Command failed with error code 106
varnishadm -S /etc/varnish/secret -T 127.0.0.1:6082 vcl.load failed

Answer 1

In 2.1 string concatenation looks like this:

set req.http.Location = "http://example.com" req.url;

In 3.0 this was done explicitly using "+".

https://www.varnish-cache.org/docs/3.0/installation/upgrade.html#string-concatenation-operator