my $str = "hello"; # no special chars, 1-127
my $sha256 = Digest::SHA::sha256("abc123"); # bytes 0-255
my $hmac = Digest::SHA::hmac_sha512("a message", "a key"); # bytes 0-255
# edit, the following is mangled by PM's editor, imagine greek letters here:
my $unicode_string = "αβγαabc123"; # unicode chars mixed with lower-ascii
my $buffer = ""; # buffer to concatenate above into and POST them
for($str, $sha256, $hmac, $unicode_string){
  $buffer .= Encode::encode("UTF-8", $_);
}
my $b64 = base64_encode($buffer);
my $HTTPheader = "ABC: $b64";
$ua->POST("aurl" ... $b64 ... $HTTPheader ...);
$ua->GET("aurl" ... $b64 ... $HTTPheader ...);
$ua->POST("aurl" ... $buffer ... $HTTPheader ...);
$ua->GET("aurl" ... $buffer ... $HTTPheader ...);
$ua->GET("aurl" ... $unicode_string ... $HTTPheader ...);

##</code><code>##

    postdata = urllib.parse.urlencode(data)
    encoded = (str(data['nonce']) + postdata).encode()
    message = urlpath.encode() + hashlib.sha256(encoded).digest()

##</code><code>##

my $postdata = Encode::encode('UTF-8', "x=1&y=2&z=greektext"); # for example, 
my $p1 = "$nonsense".'&'.$postdata; # yes & needed
my $p1_utf8 = Encode::encode_utf8($p1);
my $api_sha256 = Digest::SHA::sha256($p1_utf8);
my $message = Encode::encode_utf8($api_path)
  . Encode::encode_utf8($api_method)
  . $api_sha256; #<< last one is binary

# ... and post after some more massaging