use Time::HiRes qw( usleep );
...
while (my $c = $d->accept) {
   threads->create(\&process_one_req, $c)->detach();
   usleep(50_000);
}

##</code><code>##

use HTTP::Daemon;
use threads;

my $d = HTTP::Daemon->new(LocalAddr => $ARGV[0],
                          LocalPort => 80,
                          Reuse  => 1,
                          Listen => 20) || die;
print "Web Server started, server address: ", $d->sockhost(), ", server port: ", $d->sockport(), "\n";

while (my $c = $d->accept) {
    threads->create(\&process_client_requests, $c)->detach;
    $c->close;  # close client socket in server
}
sub process_client_requests {
    my $c = shift;
    $c->daemon->close;   # close server socket in client
    while(my $r = $c->get_request) {
        if ($r->method eq "GET") {
            my $path = $r->url->path();
            $c->send_file_response($path) or die $!;
            #or do whatever you want here
        } else { print "unknown method ".$r->method."\n" }
    }
    $c->close;
}