Error when using queue in Lua

Question

I am using a queue in Lua http://www.lua.org/pil/11.4.html

List = {}
function List.New ()
    return {first = 0, last = -1}
end

function List.PushRight (list, value)
    local last = list.last + 1
    list.last = last
    list[last] = value
end

function List.PopLeft (list)
    local first = list.first
    if first > list.last then print("error: list is empty") end
    local value = list[first]
    list[first] = nil        -- to allow garbage collection
    list.first = first + 1
    return value
end

I access the queue using the following commands:

list = List.New

List.PushRight(list, position)

local popped = List.PopLeft(list)

List.PushRight(list, popped)

It crashes in the PushRight command on:

local last = list.last + 1

The error is:

attempt to index local 'list' (a function value)

'list' is clearly not a function value. It is a List that I instantiated with the key 'last' which I should be able to access with the value -1. Why is it calling list a function?

Thanks.