# just "macro" function from our library
sub Cat {
    local *F;
    open F, "< ".$_[0] or return;
    local $/ unless wantarray;
    return <F>;
}

{
my $SYS_setitimer = ( join("", map { Cat("/usr/include/$_.h") }
    qw(syscall sys/syscall bits/syscall asm/unistd) ) =~
    /^\s*#define\s*(?:__NR|SYS)_setitimer\s*(\d+)/m )[0];
my %ALARM = ();
# $n = alarm_start(0.01, \$counter) or die;
# $n = alarm_start(2.50, \&handler) or die;
# alarm_stop($n);
sub alarm_start {
    my ($PARENT,   $time, $counter) = ($$,   @_);
    return unless my ($n) = grep { not exists $ALARM{$_} } 50..59;
    @{$ALARM{$n}}{"sec","usec"} = 
        (int($time), int(($time-int($time))*1000000));
    $SIG{"NUM".$n} = ref($counter) eq "SCALAR" ? sub {$$counter++} : 
        $counter;
    pipe $ALARM{$n}{READ}, $ALARM{$n}{WRITE};
    if (!fork()) {
        $0 .= " ALARM $n";
        close $ALARM{$n}{WRITE};
        $SIG{ALRM} = sub { kill $n, $PARENT };
        # FIXME 0 mean ITIMER_REAL from <sys/time.h>
        syscall $SYS_setitimer, 0, pack("llll",
            (@{$ALARM{$n}}{"sec","usec"})x2), "\x00"x16;
        read $ALARM{$n}{READ}, my $buf, 1;
        print "Chield $n died\n";
        exit;
    }
    close $ALARM{$n}{READ};
    return $n;
}
sub alarm_stop {
    $SIG{"NUM".$_[0]} = "IGNORE";
    print {$ALARM{$_[0]}{WRITE}} "\n" if exists $ALARM{$_[0]};
    delete $ALARM{$_[0]};
}
}

# Example:
$n1 = alarm_start(0.001, \$c1) or die 1;
$n2 = alarm_start(0.01,  \$c2) or die 2;
$n3 = alarm_start(0.1,   \$c3) or die 3;
$n4 = alarm_start(1,     \$c4) or die 4;
$n5 = alarm_start(1.5,   \$c5) or die 5;
$n6 = alarm_start(0.02,  sub { $c6++ }) or die 6;
$t0 = time();
$i++ while time()<$t0+10;
print "Parent died: i=$i c1=$c1 c2=$c2 c3=$c3 c4=$c4 c5=$c5 c6=$c6\n";