# $data is my filehandle to read from

my ($rin,$rout,$win,$wout,$ein,$eout);   # for select
$rin=$rout=$win=$wout=$ein=$eout= '';

vec($rin, fileno($data), 1) = 1;
$ein = $rin;

my $last = time;
my $heartbeat_interval = 60;
my $timeout = 1; # for select

while (! $done) {
        $rout=$wout=$eout= '';
        my ($nfound, $timeleft) = select($rout=$rin, $wout=$win, $eout=$ein, $timeout);

        if ($nfound and $rout & $rin) {
			# read from <$data> carefully not to block
			# count statistics
        }
        my $now = time;
        if (($now - $last) >= $heartbeat_interval) {
                $last = $now;
				# do something every heartbeat_interval seconds
        }
}