use JSON::XS;
use Digest::MD5 'md5_hex';
use MIME::Base64;
my $signing_key = '//Sw0rdFiSh//';
my $data = {
first_name => 'Will',
last_name => 'Smith',
age => 39,
};
my $json_string = encode_json( $data );
my $signature = md5_hex( $signing_key . $json_string );
my $base64_encoded = encode_base64( $json_string, '' );
# Send the encoded data and the signature in the HTML as hidden fields
print <<"HTML";
HTML