Nginx: Advanced proxy_pass depending on file exists

gistfile1.nginxconf

server {
  listen 443;
  server_name my.domain.com;

  root /var/www/my.domain.com;

  ssl on;
  ssl_certificate /usr/local/etc/ssl/star.crt;
  ssl_certificate_key /usr/local/etc/ssl/star.key;

  ssl_session_timeout 5m;

  ssl_protocols SSLv3 TLSv1 TLSv1.1 TLSv1.2;
  ssl_ciphers "HIGH:!aNULL:!MD5 or HIGH:!aNULL:!MD5:!3DES";
  ssl_prefer_server_ciphers on;

  location / {
    set $path $uri;
    
    if ($http_referer ~* my\.domain\.com(.*)$) {
      set $path $1;
    }
  
    set $v1_url https://v1.domain.com;
    set $v2_url https://v2.domain.com;
    
    set $proxy_pass_url $v1_url;
    
    if (-f "/v2/$path") {  
      set $proxy_pass_url $v2_url;
      break;
    }
    
    if (-f "/v2/$path.js") { 
      set $proxy_pass_url $v2_url;
      break;
    }
    
    if (-f "/v2/$path.html") {
      set $proxy_pass_url $v2_url;
      break;
    }
    
    if (-f "/v2/$path/index.js") { 
      set $proxy_pass_url $v2_url; 
      break;
    }
    
    if (-f "/v2/$path/index.html") {
      set $proxy_pass_url $v2_url;
      break;
    }
    
    proxy_pass $proxy_pass_url;
    
    # Pass a bunch of headers to the downstream server, so they'll
    # know what's going on.
    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    proxy_set_header X-Forwarded-Host $host;
    proxy_set_header X-Forwarded-Port 443;
    proxy_set_header X-Real-IP $remote_addr;
    proxy_set_header X-Secure on;
    
    # Most web apps can be configured to read this header and
    # understand that the current session is actually HTTPS.
    proxy_set_header X-Forwarded-Proto https;
    
    # We expect the downsteam servers to redirect to the right
    # hostname, so don't do any rewrites here.
    proxy_redirect off;
    
    proxy_connect_timeout 600;
    proxy_send_timeout 600;
    proxy_read_timeout 600;
    send_timeout 600;
  }
}