use URL::Encode 'url_decode_utf8';
use utf8::all;
$string = '%E6%88%91%E7%88%B1c++';
print url_decode_utf8("$string");

##</code><code>##

 ...
 $EncodeMap{"\x20"} = '+';
 ...
 $s =~ y/+/\x20/;