$utf8 = Encode::decode('assumed-encoding-of-s', $s)

##</code><code>##

print unpack("H*", $s);

##</code><code>##

use Encode "encode";

my $a = "\x{3042}";  # hiragana 'a' == codepoint U+3042
my $a_enc = {
    # common unicode encodings
    utf8   => $a,
    ucs2be => encode("ucs2be", $a),
    ucs2le => encode("ucs2le", $a),

    # common jp legacy encodings
    sjis   => encode("sjis",   $a),
    cp932  => encode("cp932",  $a),  # MS version of shift-jis
    eucjp  => encode("eucjp",  $a),
    
    # ASCII not possible!
    ascii  => encode("ascii",  $a),  # -> renders as '?' (3f)
};

for my $encoding (sort keys %$a_enc) {
    printf "%-6s : %s\n", $encoding,
                          unpack("H*", $a_enc->{$encoding});
}

##</code><code>##

ascii  : 3f
cp932  : 82a0
eucjp  : a4a2
sjis   : 82a0
ucs2be : 3042
ucs2le : 4230
utf8   : e38182

##</code><code>##

$html_entity = '&#x'.unpack("H*", encode("ucs2be", $ch)).';';