"\u" is a known escape sequence (meaning "uppercase"), so you need to write "\\u" or '\u' instead: 
use Encode;
use strict;
use warnings;
use 5.010; # only required for say(), not for the encoding stuff

binmode STDOUT, ':encoding(UTF-8)';

$_ = "\\u6b63";
$_ =~ s/\\u(.{4})/chr(hex $1)/eg;

say $_;

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See also: Perl and Unicode.

Perl 6 - links to (nearly) everything that is Perl 6.

In reply to Re: unicode/utf string to actual character by moritz
in thread unicode/utf string to actual character by xachen

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