It does not look like JSON::RPC::Client does 2.0, I found JSON::RPC::Common on CPAN which appears to, here is a code snippet for that: 

#!/usr/bin/perl

use strict;
use warnings;
use Data::Dumper;
use JSON::RPC::Common::Marshal::HTTP;
use LWP::UserAgent;

my $ua = LWP::UserAgent->new;

my $req_data = {
        jsonrpc => "2.0",
        method  => "user.authenticate",
        id      => "xxx",
        params  => { user=>'yyy', password=>'zzz' },
};
my $req_obj = JSON::RPC::Common::Procedure::Call->inflate($req_data);

my $m = JSON::RPC::Common::Marshal::HTTP->new;
my $req = $m->call_to_request($req_obj);
$req->uri('http://zabbix/api_jsonrpc.php');

my $res = $ua->request($req);

my $res_obj = $m->response_to_result($res);
print Dumper($res_obj);

[download]

In reply to Re^4: Grappling with JSON::RPC::Client by reenen
in thread Grappling with JSON::RPC::Client by Garp

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.