send multiple requests instead of one at a time

Apparently my little program,

    my $r = HTTP::Request->new(
        HEAD => undef,
        [ 'If-Modified-Since' => time2str( time - 60 * 60 * shift @ARGV ) ]
    );
    my $ua = LWP::UserAgent->new;
    $ua->env_proxy;
    while (<>) {
        $r->uri($_);
        print if ( $ua->request($r)->code == RC_NOT_MODIFIED );
    }

would be more efficient if it just sent one big request. I read the
undated but Last-Modified: Apr 2000 paper,
http://linpro.no/lwp/lwpng-paper/ , but of course still don't know
what to do next. I even read LWP::ConnCache but cannot picture in my
mind any examples.

P.S., http://linpro.no/lwp/ should mention
http://news.gmane.org/group/gmane.comp.lib.libwww/
instead of those outdated other places.