Relative file paths in Lua scripts?

I have a directory containing my dissector, listener, and subdirectories with libraries. I've been attempting to use dofile, require, and filepath strings to call the libraries along with additional files like so:

dofile("subdirec/script.lua")
require "subdirec.script"
local filename = "subdirec/file.xml"

However, when I attempt using this syntax and open Wireshark I get the “file does not exist error”.