Examples of Lua in Redis (http://www.redisgreen.net/library.html); also there is a nice tutorial (http://www.redisgreen.net/blog/intro-to-lua-for-redis-programmers/)

ratelimit.lua

-- http://www.redisgreen.net/library/ratelimit.html

-- Return Value: 1 if rate limit exceeded, otherwise 0
-- Keys: 1
--  1. A key to use as an expiring counter, e.g. "ratelimit:ip:127.0.0.1"
-- Args: 2
--  1. Maximum number of calls
--  2. Amount of time in ms

local cnt = redis.call('INCR', KEYS[1])
if cnt > tonumber(ARGV[1])
then
	return 1
end
if cnt == 1
then
	redis.call('PEXPIRE', KEYS[1], ARGV[2])
end
return 0

runningavg.lua

-- http://www.redisgreen.net/library/runningavg.html

-- Return Value: the new average value
-- Keys: 2
--  1. Key to store the current average.
--  2. Key to store the current count of values.
-- Args: 1
--  1. The next value in the series

local currentval = tonumber(redis.call('get', KEYS[1])) or 0
local count = redis.call('incr', KEYS[2])

currentval = tostring(currentval * (count - 1)/count + (ARGV[1]/count))

redis.call('set', KEYS[1], currentval)
return currentval

smemhashes.lua

-- http://www.redisgreen.net/library/smemhashes.html

-- Return Value: Multi-Bulk - a list of hashes by key
-- Caveat: This script violates the EVAL command semantics and should not be considered safe for Redis Cluster.
-- Keys: 1
--  1. A Set containing the keys of a series of Hashes.
-- Args: None

local keys = redis.call("smembers", KEYS[1])
local ret = {}
for k,v in pairs(keys) do 
  ret[k] = {v, redis.call("hgetall", v)}
end
return ret