let s:pairs = ['{}', '()', '[]']
function! s:autoPair()
  let line = getline('.')
  let col = col('.')
  let before = line[col - 2:col - 2]
  let after = line[col - 1:col - 1]
  for pairStr in s:pairs
    if pairStr[0] == before &&
     \ pairStr[1] == after
      return "\<CR>\<CR>\<Up>\<Esc>cc"
    endif
  endfor
  return "\<CR>"
endfunction
for pairStr in s:pairs
  execute printf("inoremap <expr> %s '%s<\Left>'",
               \ pairStr[0],
               \ pairStr)
endfor
inoremap <expr> <CR> <SID>autoPair()