#!/your/perl/here

use strict;
use warnings;

my @paths = (
          'C:\\foo\\bar\\baz',
          'C:\\foo\\bar',
          'C:\\car',
          'C:\\c'
        );

# remove duplicates
my %paths;
@paths{@paths} = (1) x @paths;

# create the tree of paths seen
my $tree = {};
foreach my $path ( keys %paths )
{
	my @dirs = split /\\+/, $path;
	
	# insert in hash
	my $node = $tree;
	foreach my $dir ( @dirs )
	{
		if ( exists( $node->{LEAF} ) )
		{
			print "$path\n";
		}
		# create the next nested hash if needed
		$node->{$dir} = {} unless exists $node->{$dir};
		# move pointer down a level
		$node = $node->{$dir};
	}
	# if there are keys at this level (other than LEAF)
	my $keys = keys %{$node};
	if ( ( $keys > 1 )
	  or ( ( $keys == 1 )
	   and ( exists $node->{LEAF} ) ) )
	{
		print "$path\n";
	}
	# mark this as a leaf
	$node->{LEAF}=1;
}

__OUTPUT__
C:\foo\bar\baz

##</code><code>##

      $nested{$path} = 1;