I couldn't get RPC::XML::Client to work right, so I used Frontier::Daemon instead:

#!/usr/bin/perl 

use strict;
use warnings;
use Frontier::Daemon;

my $d = Frontier::Daemon->new(
                   methods => {
                          sum => \&sum
                          },
                   LocalAddr => '127.0.0.1',
                   LocalPort => 1080,
                   );       

sub sum {
   my @args = (9, 9);
   print "The numbers to be added are: @args\n";
   return $args[0] + $args[1], "\n";
}
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Update: I used WebService::Advogato by jaldhar to make a simple sum, product, and square client:

#!/usr/bin/perl
#sum, product, square

use strict;
use warnings;
use Data::Dumper::Concise;
use WebService::Advogato;

my $client = new WebService::Advogato();           
my $int_x = '91';
my $int_y = '23';
warn Dumper($client->sumprod($int_x, $int_y));
warn Dumper($client->square($int_x));
[download]