proxy_store

[SplitIce]

Been tearing out my hair for hours today trying to get proxy_store to
work. Is there a minimum version for proxy_store with variables
support?

My nginx refuses to work with simple stuff like
set $md5 test;
proxy_store /data/nginx/1/$md5;"

instead trying to store to [root]/[full url] evident by the error log
2012/06/28 17:13:24 [error] 5700#0: *1 open()
"/usr/html/img/diagram.png" failed (2: No such file or directory),
client: 192.168.2.2, server: , request: "GET /img/diagram.png
HTTP/1.1", host: "192.168.2.15:88"

My nginx version 1.2.1

I dont see it in the changelog, howeaver maybe its a new feature? Not
in stable that is.