Interactive console for Lua 5.1

console.lua

--[[
Usage:

-- Start a console instance, holds its own environment
local console = InteractiveConsole {
    sum = function(a, b)
        return a + b
    end
}
-- First call: define output and error functions
console(print, error)

-- Following calls: whatever the user types in
console 'a = {'
console '   5, 6
console '}'
console 'print(sum(unpack(a)))' --> 11
]]

local function InteractiveConsole(env)
    return coroutine.wrap(function(out, err)
        local sandbox = setmetatable({ },
            {
                __index = function(t, index)
                    return rawget(t, index) or env[index] or _G[index]
                end
            }
        )
        sandbox._G = sandbox
        sandbox.os = { }
        sandbox.io = { }
        sandbox.debug = { }    
        sandbox.error = err
        sandbox.print = function(...)
            local r = {}
            for _, v in ipairs({...}) do
                table.insert(r, tostring(v))
            end
            local s = table.concat(r, string.rep(' ', 4))
            return out(#s > 0 and s or 'nil')
        end    
 
        local chunks = {}
        local level = 1
 
        while true do
            table.insert(chunks, coroutine.yield())
 
            local func, e = loadstring(table.concat(chunks, ' '), 'console')
            if func then           
                setfenv(func, sandbox)
                out(string.rep('>', level) .. ' ' .. chunks[#chunks])
                local s, e = pcall(func)
                if not s then
                    err(e)
                end
 
                chunks = { }
                level = 1
            else
                if not e:find('near \'<eof>\'$') then
                    chunks = { }
                    level = 1
                    err(e)
                else                   
                    out(string.rep('>', level) .. ' ' .. chunks[#chunks])
                    level = 2
                end
            end
        end
    end)
end

Missing trailing ' at line 15.