G'day darkblackblue,

This looks like you're running into a backslashitis nightmare. I think I'd aim for something closer to:

my $path_base = 'C:\Users\darkblack\Desktop\A\.';
...
my $dir = $path_base . $directory_name;
[download]

I don't have an MSWin box to test this on; however, the basic concept works fine on my system:

$ pwd
/Users/ken/tmp
$ ls -al .fred
ls: cannot access '.fred': No such file or directory
$ perl -e 'my $x = q{/Users/ken/tmp/.}; my $y = q{fred}; mkdir $x . $y
+'
$ ls -al .fred
total 0
drwxr-xr-x  2 ken staff  68 Dec  4 18:27 .
drwxr-xr-x 19 ken staff 646 Dec  4 18:27 ..
[download]