use LWP::UserAgent;

my $ua = LWP::UserAgent->new;
$ua->proxy(['http', 'ftp'] => 'http://proxy.myorg.com');

my $req = HTTP::Request->new('GET',"http://www.perl.com");
$req->proxy_authorization_basic("proxy_user", "proxy_password");

my $res = $ua->request($req);
print $res->content if $res->is_success;