Your proxy.pac should have the host in it. It seems to me that you might want to have a look at that. Also, you'll need to use a module like Data::Dumper or one of the other modules in that namespace to get a look at your results. Here's what I tried. I borrowed the proxy.pac from the test directory:

proxy.pac

function FindProxyForURL(url,host)
{
    // loopback
    if ( host == "127.0.0.1" || host == "localhost" )
        return "DIRECT";

    if ( dnsDomainIs(host, "intra.example.com") )
        return "PROXY proxy.example.jp:8080; DIRECT";
    if ( isInNet(host, "192.168.108.0","255.255.255.0") )
        return "DIRECT proxy.example.jp:8080";
    return "PROXY";
}
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And the script that I came up with:

proxy_pac.pl

#!/usr/bin/perl

use strict;
use warnings;
use HTTP::ProxyPAC;
use LWP::UserAgent;
use Data::Dumper::Perltidy;

my $accessor = '/root/Desktop/proxy.pac';

my $ua = LWP::UserAgent->new(timeout => 30);  
undef $ua; 

my $pac = HTTP::ProxyPAC->new($accessor);
print Dumper(
  my $res = $pac->find_proxy(
     'http://www.intra.example.com/')
);
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