set $cookie_abc "$cookie_abc";

[amodpandey]

The variable $cookie_abc will exist only if the client request cookie has
"abc". In my case the first request won't have this cookie set and I am
setting this value for some magic.

Lua module is very this on this feature. If we do not have the variable
defined you should set it before using.

set $cookie_abc "$cookie_abc"

If the above works as expected I am good.

Posted at Nginx Forum: http://forum.nginx.org/read.php?2,236075,236108#msg-236108