use File::Find;
use File::Basename;
use File::Spec;
use strict;

find ({ 'wanted' => \&renamefile }, 'c:\\folder1\\folder2');

sub renamefile {
    my $file = $_;
    return unless (-f $file);
    my $dirname = dirname($file);
    my $file_name = basename($file);
    my $new_file_name = $file_name;
    $new_file_name =~ s/\\\\/./g;

    print "\$file = [$file]\n";

	my $resulting_filename = File::Spec->catfile($dirname,$new_file_name);
    print "\$resulting_filename = [$resulting_filename]\n";

    rename($file,File::Spec->catfile($dirname,$new_file_name))or die;
}

C:\Steve\Dev\PerlMonks\P-2013-08-06@1508-Rename-Fail>perl renameFailDebug.pl
$file = [abc.txt]
$resulting_filename = [abc.txt]