#!/usr/bin/perl -w

use strict;
use File::Find;

find(\&wanted,'.');

use vars qw(%dirseen);
sub wanted
{
  return unless -d $_;

  if ($dirseen{$_})
  {
    print "Duplicate directory name $_ in $File::Find::dir\n";
  }
  $dirseen{$_}++;
}
[download]

Thanks for this information. It saved a big headache. Now I've got to go in and rename the duplicates with a one-up sequence number appended to the directory name. I'm hoping that 'rename' will work on directories.

rename will work fine on directories as long as they're on the same filesystem.

File::Find is good for this sort of thing,

use File::Find;
my @dupes;
{
    my %dirnames;
    sub dupe_dir {
        -d or return;
        if (exists $dirnames{$_}) {
            push @dupes, $File::Find::name;
        }
        else {
            ++$dirnames{$_}
        }
        1;
    }
}

find(\&dupe_dir)
print $_, $/ for @dupes;
[download]

Are you sure they're duplicates?
Unless I'm very much mistaken, (certainly on UNIX) you cannot have files/directories/special files with the same name in a given directory.

Update:
Doh! Across an entire directory tree it's possible (obviously) to have duplicated names.
You should probably look at $File::Find::dir and $File::Find::name from File::Find's wanted() method to distinguish between a non-uniquely named files/directories by location.

Update 2: Use a hash.

This can be handled neatly with File::Find::Rule as well, which is a nicer interface to File::Find:

#!/usr/bin/perl -l

use File::Find::Rule;
print foreach File::Find::Rule
  ->directory
  ->exec(sub { $seen{$_}++ })
  ->in(shift || ".");
[download]

Tony