use Fcntl;

my $countfile = 'kontaktcount.txt';
sysopen(COUNT, $countfile, O_RDWR|O_CREATE) or die $!;
flock(COUNT, 2) or die $!;
my $count = <COUNT> || 0;
chomp($count);
seek(COUNT, 0, 0) or die $!;
truncate(COUNT, 0, 0) or die $!;
print COUNT ++$count;
close(COUNT);