tmux使用時vimでインサートモードの時カーソルの形を変える

if exists('$TMUX')
  let &t_SI = "\<Esc>Ptmux;\<Esc>\<Esc>]50;CursorShape=1\x7\<Esc>\\"
  let &t_EI = "\<Esc>Ptmux;\<Esc>\<Esc>]50;CursorShape=0\x7\<Esc>\\"
else
  let &t_SI = "\<Esc>]50;CursorShape=1\x7"
  let &t_EI = "\<Esc>]50;CursorShape=0\x7"
endif