-- load the requested file
chunk = loadfile("FILENAME");

-- Remember what is defined in global scope
g={}
for n in pairs(_G) do
  g[n]=true
end

-- execute the loaded chunk
chunk();

-- Now look again what is defined, pick only functions and print their names
for n in pairs(_G) do
  if (not g[n] and type(_G[n])=='function') then
    print(n)
  end
end