I recommend the previously stated Data::Dumper solution, since it handles not only strings of bytes, but UNICODE strings too.

>perl -e"use Data::Dumper; $Data::Dumper::Useqq = 1; print Dumper qq{\
+x{400}};"
$VAR1 = "\x{400}";
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If you were dealing with bytes, you could use unpack 'H*'

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