function! RubyRC(start, end)
  let source = join(getline(a:start, a:end), "\n")

  split
  call term_start(['ruby', '-e', source], { 'curwin': v:true, })
endfunction

vnoremap <silent> mm :call RubyRC(line("'<"), line("'>"))<CR>
nnoremap <silent> MM :call RubyRC(1, '$')<CR>