use strict;
use warnings;
use File::Basename qw( fileparse );

my %seen;
while (<DATA>) {
    (undef, my $path) = fileparse( $_ );
    print "$path\n" unless $seen{$path}++;
}

print "="x70,"\n";

foreach my $key (keys %seen){
    print "$key\n" if 1 == scalar grep { /\Q$key/ } keys %seen;
}
__DATA__
testing123/
foobar/
helloworld/
helloworld/r1/
helloworld/r1/helloworld-5-0.noarch.rpm
helloworld/r1/testfile23.txt
helloworld/r1/tomcat-7.0.27.rpm
helloworld/r2/
helloworld/r2/helloworld-2-0.noarch.rpm
helloworld/r2/testfile12.txt
helloworld/r2/tomcat-5.0.52.rpm
hellotest/

##</code><code>##

use strict;
use warnings;
use File::Basename qw( fileparse );

my %seen;
my @directories;
while (<DATA>) {
    (undef, my $path) = fileparse( $_ );
    #push @directories, $path;  
    ## update, I indended to put the push inside the unless block.
    ## The original works but not exactly as I expected since it puts
    ## duplicates in the array. 
    #print "$path\n" unless $seen{$path}++;
    unless ($seen{$path}++) {
        print "$path\n";
        push @directories, $path;
    }
}

print "="x70,"\n";

foreach my $index (0..$#directories-1){
    my $current = $directories[$index];
    print "$current\n" if not $directories[$index+1] =~ /\Q$current/ ;
}
### assuming the last one is always terminal
print $directories[$#directories], "\n"; 
__DATA__
testing123/
foobar/
helloworld/
helloworld/r1/
helloworld/r1/helloworld-5-0.noarch.rpm
helloworld/r1/testfile23.txt
helloworld/r1/tomcat-7.0.27.rpm
helloworld/r2/
helloworld/r2/helloworld-2-0.noarch.rpm
helloworld/r2/testfile12.txt
helloworld/r2/tomcat-5.0.52.rpm
hellotest/

##</code><code>##

use strict;
use warnings;
use File::Basename qw( fileparse );

my $first='';
my $second='';

while (<DATA>) {
    $first = $second;
    (undef, $second) = fileparse( $_ );
    print "$second\n" if eof DATA;  
    next unless $first;
    unless ( $second =~ /\Q$first/) {
        print "$first\n";
    }
}


__DATA__
testing123/
foobar/
helloworld/
helloworld/r1/
helloworld/r1/helloworld-5-0.noarch.rpm
helloworld/r1/testfile23.txt
helloworld/r1/tomcat-7.0.27.rpm
helloworld/r2/
helloworld/r2/helloworld-2-0.noarch.rpm
helloworld/r2/testfile12.txt
helloworld/r2/tomcat-5.0.52.rpm
hellotest/test.txt
hellotest/