my $string_to_sign = 'POST&%2F&'.$ua->www_form_urlencode( $data );
my $key = '<accessSecret>' . '&';
my $signature = hmac_sha1_base64($string_to_sign, $key);
while (length($signature) % 4) {
  $signature .= '='; # padding
}
$data->{'Signature'} = $signature;
printf "str = %s\n",$string_to_sign;
printf "sig = %s\n",$signature;