#!/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;
    }
}

##</code><code>##

1474530606.74812
0
1
2
1474530607.75322
3
4
5
1474530608.75744
6
1474530608.75752
7
8
9
1474530609.75927
10
11

##</code><code>##

last unless @packets;
my $line = shift @packets;

##</code><code>##

last if eof $fh;
my $line = <$fh>;

##</code><code>##

ualarm 1 if $line == 6;