$s = '\u805a\u5408\u6216\u8be6\u7ec6';
$s =~ s/u(\w\w\w\w)/x{$1}/g; 
$s = eval qq{"$s"};
print($s);

##</code><code>##

$s = '\u805a\u5408\u6216\u8be6\u7ec6';
$s =~ s/\\u([0-9A-Fa-f]{4})/chr(hex($1))/ge;
print($s);