I'm trying to make a simple request to bitcoind using perl I followed the example from the API reference, but it fails saying "401 Authorization Required"

#!/usr/bin/perl -w 

use JSON::RPC::Client;
use Data::Dumper;

my $client = new JSON::RPC::Client;

$client->ua->credentials(
    'localhost:8332', 'jsonrpc', 'bitcoinrpc' => 'mybitcoinrpcpassword'  # REPLACE WITH YOUR bitcoin.conf rpcuser/rpcpassword
    );

my $uri = 'http://localhost:8332/';
my $obj = {
    method  => 'getinfo',
    params  => [],
};

my $res = $client->call( $uri, $obj );

if ($res){
    if ($res->is_error) { print "Error : ", $res->error_message; }
    else { print Dumper($res->result); }
} else {
    print $client->status_line;
}

Am I missing something obvious? Thanks for any help!