StackExchange.Redis Lua script error in for loop - lua

Question

I am facing a problem with the Lua script (please find it below) in the StackExchange.Redis.
I have dissected the code and got all of it working except for the last loop.
I get the following as error -- ERR Protocol error: expected '$', got ' '
The error message is quite generic in nature, as it gives me the same error message for different types of errors.
Can someone help me to figure out the problem?
var doesExist = (bool)db.ScriptEvaluate(#"
local function isDateInRange(DateStart, DateEnd, GivenDate)
if (GivenDate > DateStart and GivenDate < DateEnd)
then
return(true)
else
return(false)
end
end
--Fetch User's Category's StartDate and EndDate
local function IsCategoryDateValid()
local givenDate, DateStart, DateEnd
GivenDate = '2017-01-09'
StartDate = '2015-01-01'
EndDate = '2018-01-01'
local isDateValid
isDateValid = isDateInRange(StartDate, EndDate, GivenDate)
return(isDateValid)
end
-- Pass User, UserCategory and UserCategoryItem as parameters
local userNameKey = 'UserDetails:Invincible'
local userCategoryKey = 'UserCategories:Book'
local userCategoryItemKey = 'UserCategoryItems:Harry-Potter'
local userNameKeySplit = {}
local a = 1
for i in string.gmatch(userNameKey, '([^'..':'..']+)') do
userNameKeySplit[a] = i
a = a + 1
end
local userName = userNameKeySplit[2]
local userCategoryKeySplit = {}
local b = 1
for j in string.gmatch(userCategoryKey, '([^'..':'..']+)') do
userCategoryKeySplit[b] = j
b = b + 1
end
local userCategory = userCategoryKeySplit[2]
local userCategoryItemKeySplit = {}
local c = 1
for k in string.gmatch(userCategoryItemKey, '([^'..':'..']+)') do
userCategoryItemKeySplit[c] = k
c = c + 1
end
local userCategoryItem = userCategoryItemKeySplit[2]
-- Fetch Users, UserCategories and UserCategoryItems from the Redis DB
local userData = {'Invincible', 'User1', 'User2', 'User3'}
local userCategoryData = {'Book', 'Movie', 'Journals'}
local userCategoryItemData = {'Hardy-Boys', 'Harry-Potter', 'Shawshank-Redemption', 'The-Terminal'}
local msg
for i=1,#userData,1
do
if(userData[i] == userName)
then
for j=1,#userCategoryData,1
do
if(userCategoryData[j] == userCategory)
then
msg = true
break
else
msg = false
end
end
break
else
msg = false
break
end
end
return msg
",
new RedisKey[] { "UserDetails:" + "Invincible", "UserCategories:" + "Book", "UserCategoryItems:" + "Harry-Potter" });