1) Use loadstring() to compile and run a script from a Redis key.
EVAL "return loadstring(redis('get', KEYS))()" 1 foo
2) Set a function as a global value, and call that.
EVAL "myfunc = function() return 42" 0
EVAL "return myfunc()" 0
antirez said in his previous post (http://antirez.com/post/redis-and-scripting.html) that storing scripts has some problems with regard to Redis Cluster, though.