use strictures;
use CGI ":standard";
use HTML::Entities;

# Called https://mysite/cgi-bin/rpc.pl?args=to;the=call
my $explicitly_scalar_param = param("args");
my $the = param("the");

print header(),
    start_html("Title..."),
    h1("header"),
    div("Do something safely with",
        encode_entities($explicitly_scalar_param),
        "and",
        encode_entities($the)),
    end_html;

# Test on command line: ./rpc.pl 'args=to;the=call'

##</code><code>##

use strictures;
use Plack::Request;
# Called https://mysite/not-the-cgi-bin/rpc.pl?args=to;the=call

sub {
    my $req = Plack::Request->new(+shift);
    my $args = $req->parameters->{args};
    my $the = $req->parameters->{the};
    [ 200,
      [ "Content-Type" => "text/html" ],
      [ "HTML tags + output. You HTML encode ALL unknown data." ]
    ];
};

# Command line: plackup rpc.pl
# HTTP::Server::PSGI: Accepting connections at http://0:5000/
#                           -> port 5000 on localhost ^^^