Toggle between tabs and spaces

gistfile1.txt

function! ToggleTab()
  if &expandtab
    set shiftwidth=8
    set softtabstop=0
    set noexpandtab
  else
    execute "set shiftwidth=".g:my_tab
    execute "set softtabstop=".g:my_tab
    set expandtab
  endif
endfunction
nmap <F9> mz:execute ToggleTab()<CR>'z