#!/usr/bin/perl
use warnings;
use strict;


for (my $i = 1; $i <= 10000; $i++) {
	open (F1, ">:encoding(UTF-8)", "rename1.txt") or die "Can't open file1: $!";
	open (F2, ">:encoding(UTF-8)", "rename2.txt") or die "Can't open file2: $!";

	print F1 "File one";
	print F2 "File two";

	close F1;
	close F2;
	
	# unlink "rename2.txt";    # error occurs even if you unlink the file first, although less often
	
	rename ("rename1.txt", "rename2.txt") or die "Can't rename file: $!";
	print "loop $i done\n\n";
}