solutions = {
  [[return input:upper()]],
  [[return input:lower()]],
}

local left, right = input:match('^(.*)=(.*)$')
if not left then
  return "Please enter a transformation example, e.g. abc=ABC"
end

input = left -- so the solutions get the right input

for _, code in ipairs(solutions) do
    f = load(code)
    log("loaded code: "..tostring(f))
    s = f() -- TODO: use pcall
    log("result: "..tostring(s))
    if s == right then
        return "Solution found:\n\n"..code
    end
end

return "Sorry, no solution found..."