# trying to optimize performance and memory usage 
# by replacing foreach() with while()

	my $file     = "./test.txt";
	my $tempfile = "./tempfile".(rand()*9999);

	open (LOG, $file);
	flock LOG, 1;

	open (TMP, ">$tempfile");
	flock TMP, 2;

	while (my $line = <LOG>){
		# here we do some manipulations with $line
		print TMP $line;
	}
	close TMP;
	rename($tempfile,"$file");
	close LOG;