Alejandro Camarillo:
local function mousePress(eventobj)

  if eventobj:getButtonState(2) and eventobj:getButtonState(4) then
    print("middle&left")
    hs.eventtap.event.newKeyEvent({'ctrl'}, 'up', true):post()
    hs.eventtap.event.newKeyEvent({'ctrl'}, 'up', false):post()

  elseif eventobj:getButtonState(2) and eventobj:getButtonState(3) then
    print("middle&right")
    hs.eventtap.event.newKeyEvent({'ctrl'}, 'down', true):post()
    hs.eventtap.event.newKeyEvent({'ctrl'}, 'down', false):post()

  elseif eventobj:getButtonState(4) then
    print("left")
    hs.eventtap.event.newKeyEvent({'ctrl'}, 'left', true):post()
    hs.eventtap.event.newKeyEvent({'ctrl'}, 'left', false):post()

  elseif eventobj:getButtonState(3) then
    print("right")
    hs.eventtap.event.newKeyEvent({'ctrl'}, 'right', true):post()
    hs.eventtap.event.newKeyEvent({'ctrl'}, 'right', false):post()
  end

  return false
end

hs.eventtap.new({25}, mousePress):start()