Vim call Dictionary.app on Mac

dict.vim

function! s:dict(...)
  let is_macunix = has('mac') || has('macunix') || has('gui_macvim') || (!executable('xdg-open') && system('uname') =~? '^darwin')
  if(!is_macunix)
    echohl WarningMsg
    echomsg 'Your platform is not supported!'
    echohl None
    finish
  endif
  let word = len(a:000) == 0 ? input('Dictionary search: ', expand('<cword>')) : join(a:000, ' ')
  call system(printf("open dict://'%s'", word))
endfunction
command! -nargs=* Dict call <SID>dict(<f-args>)