$ LANG=ru_RU.UTF-8 perl -CS -MEncode=decode -E '
  sub show {
    printf "is_utf8=%d, length=%d, msg=%s\n",
      utf8::is_utf8($_), length, $_;
  }
  $_=$!=111;
  show();
  $_=decode("UTF-8", $_);
  show();
'
is_utf8=0, length=40, msg=Ð Ñоединении оÑказано
is_utf8=1, length=21, msg=[here should be correct Russian "connection refused" but perlmonks's parser turn it into html entities]