The meaning of two proxy_pass directives

[speedfirst]

I saw some nginx configs written like this:

location ~ {
 ...
 proxy_pass http://upstream1;
 proxy_pass http://upstream2;
 ...
}

What this config meaning? proxy_pass to upstream2 if proxy_pass to
upstream fails?

Thanks.

Posted at Nginx Forum: http://forum.nginx.org/read.php?2,209883,209883#msg-209883