use strict;
use warnings;

use IO::Select;
use IO::Socket;
use POSIX   qw< :signal_h >;


my $port = 6681;

my $listen = IO::Socket::INET->new(
    Proto       => "tcp",
    LocalPort   => $port,
    Listen      => 10,
    Timeout     => 10,
) or die "Can't bind socket to port $port: $!";

my $select = IO::Select->new($listen);

print STDERR "listing on port $port\n";

my $alarm_handler = sub {
    print STDERR "! alarm handler\n";
    alarm(2);
};

my $sigset = POSIX::SigSet->new(SIGALRM);
my $sa_alarm = POSIX::SigAction->new($alarm_handler, $sigset, SA_RESTART);
sigaction(SIGALRM, $sa_alarm);
#$SIG{ALRM} = $alarm_handler;
alarm(2);

while (my @ready = $select->can_read) {
    for my $fh (@ready) {
        if ($fh == $listen) {
            my $sock = $listen->accept;
            $select->add($sock);
        }
        else {
            # ...
        }
    }
}