>perl -e"use Data::Dumper; $Data::Dumper::Useqq = 1; print Dumper qq{\x{400}};"
$VAR1 = "\x{400}";

##</code><code>##

>perl -le"$h = uc unpack 'H*', qq{123\t\n}; $h = ~ s/(..)/$1 /g; print $h"
31 32 33 09 0A