If, with an empty directory, you try something like:

  use File::Path;
    foreach my $n ( 0 .. 12 ) {
      mkpath("/blah/$n", 1, 0755) or die "$n: $!";
  }
[download]

output of the script:

mkdir /app/docs/intranet/Jupiter Media Metrix/mmf/1999/0
mkdir /app/docs/intranet/Jupiter Media Metrix/mmf/1999/1
mkdir /app/docs/intranet/Jupiter Media Metrix/mmf/1999/2
mkdir /app/docs/intranet/Jupiter Media Metrix/mmf/1999/3
mkdir /app/docs/intranet/Jupiter Media Metrix/mmf/1999/4
mkdir /app/docs/intranet/Jupiter Media Metrix/mmf/1999/5
mkdir /app/docs/intranet/Jupiter Media Metrix/mmf/1999/6
mkdir /app/docs/intranet/Jupiter Media Metrix/mmf/1999/7
mkdir /app/docs/intranet/Jupiter Media Metrix/mmf/1999/8
mkdir /app/docs/intranet/Jupiter Media Metrix/mmf/1999/9
mkdir /app/docs/intranet/Jupiter Media Metrix/mmf/1999/10
mkdir /app/docs/intranet/Jupiter Media Metrix/mmf/1999/10: File exists
+ at throw.pl line 8
[download]

the spaces in the directory have no effect. I've tried with non-spaced dir paths... same thing.

and the file 10 is created. strings was a great idea... here's it's output:

legal.html
images
1998
1999
2000
2001
index.html
Media: No such file or directory
[download]

those are all directories or files involved in the copying (from the non-test script!). no idea how that info is getting into the test script's output.

I'm going to go lie down now for a bit... :)

You might be able to narrow this further, but testing for the existence of the errant file prior to each step. Try the equivalent of:

  use File::Path;
    foreach my $n ( 0 .. 12 ) {
      print "/blah/10 exists prior to step $n\n"
        if -e "/blah/10";
      mkpath("/blah/$n", 1, 0755) or die "$n: $!";
  }
[download]

edit: better outputs below. dummied up the dir names, but realized the output of strings indicated some dependancies.