use feature qw/say unicode_strings/;
  use open qw/:std :utf8/;
  use Encode qw/decode encode/;
  ...
  my($row)    = $sth -> fetchall_hashref('id');
  my($name)   = $$row{100}{name};
  my($decode) = decode('utf8', $name);
  my($json)   = JSON::XS -> new -> utf8(0) -> encode({name => $decode});

  say "name:   $name.";
  say "decode: $decode.";
  say "json:   $json.";