... create sockets ...
my @fileno = (fileno(SOCKET1),
              fileno(SOCKET2),
              fileno(SOCKET3),
              fileno(SOCKET4));
my ($rbits, $ebits);
vec($rbits, $_, 1) = 1 for @fileno;
vec($ebits, $_, 1) = 1 for @fileno;
while (1) {
    my $time_to_next_heartbeat = ...;  # How long till we have to send a hb
    if ($time_to_next_heartbeat <= 0) {
        ... send heartbeats ...
        redo;
    }
    if (select (my $rbits = $rbits, undef, my $ebits = $ebits, $time_to_next_heartbeat)) {
        if ($ebits) {
            ... deal with errors ...
        }
        if ($rbits) {
            foreach my $fileno (@fileno) {
                if (vec($rbits, $filen0, 1)) {
                    ... read data ...
                }
            }
        }
    }
}