~/.xmonad: Swap key map using xkbswap.

.xmonad/xmonad.hs

(??) = flip fmap
main = do
    kbMap <- newIORef "us"
    xmonad $ defaultConfig {
        modMask  = mod4Mask,
        terminal = "sakura",
        ((0, xF86XK_AudioRaiseVolume), spawn "amixer set Master 5%+"),
        ((mod4Mask .|. shiftMask, xK_m), spawnHere "quodlibet"),
        ((mod4Mask .|. shiftMask, xK_Tab), changeKbMap kbMap),
        ((mod4Mask .|. shiftMask, xK_Tab), spawn "xkbswap"),
        ((mod4Mask .|. shiftMask, xK_l), spawn "slock"),
        ((mod4Mask, xK_q), restart "xmonad" True)
     ]
  where changeKbMap kbMap = do
          kb <- readIORef kbMap
          let switchLang cur = if cur == "us" then "de" else "us"
          spawn $ "setxkbmap " ++ switchLang kb
          modifyIORef kbMap switchLang