Flushing the serial input port with PERL

sub initSerialPort {
	local $portnum = shift;
	local $serdev = "ttyS" . $portnum;
	print "$serdev\n";
	local $serport;
	open ( $serport, "+</dev/$serdev") || die "cannot open serial port $serdev: $!\n";
	system ("stty 2400 raw </dev/$serdev");
	system("stty -F /dev/$serdev -a > $serdev-config.txt");
	return $serport
}
 
sub readUntil {
	my $port = shift;
	my $pat = shift;
	my $data = "";
	my $buf = "";
	my $br;
	my $timeout = 10000;
 
	do {
		$br = sysread($port, $buf, 256);
		$data.=$buf if $br > 0;
	} while ( $data !~ /$pat/i && $timeout--);
 
	return $data;