my $timeout = 10;   # Seconds to wait, before printing
select *STDOUT; $| = 1; # Set standard output to auto flush
while (1) {
    my $buf = my $in = '';
    eval {
        local $SIG{ALRM} = sub { print $buf,$in; die };
        while (1) {
            alarm $timeout; sysread *STDIN, $in, 500 or exit; alarm 0;
            ($buf) = ($buf.$in) =~ m/((.*?\n){0,4}.*?\n?)$/; $in = '';
        }
    }
}