#!/usr/bin/env perl -l

use strict;
use warnings;

use Time::HiRes qw{ualarm time};

my $timeout = 1_000_000; #microseconds
my $limit = 3;
my @packets = (0 .. 11);
print time;

{
    my $local_limit = $limit;

    local $SIG{ALRM} = sub {
        print time;
        $local_limit = $limit;
        ualarm $timeout;
    };

    ualarm $timeout;

    while (1) {
        next unless $local_limit-- > 0;
        last unless @packets;
        my $line = shift @packets;
        ualarm 1 if $line == 6;
        print $line;
    }
}