use strict;

my $lastline;

while (<DATA>) {
  chomp;

  unless (/^\Q$lastline\E/) {
    print $lastline,"\n";
  };
  
  $lastline = $_;  
};

# Assuming that the last line read will always
# be relevant
print $lastline;

__DATA__
CHILD: Topology/IPClassA
CHILD: Topology/IPClassA/Device
CHILD: Topology/IPClassA/Device/log_ratio
CHILD: Topology/IPClassA/Device/poll_interval
CHILD: Topology/IPClassA/Device = 2
CHILD: Topology/IPClassA/Device = 2/poll_interval
CHILD: Topology/IPClassA/Device = 2/is_managed
CHILD: Topology/IPClassA/Device = 2/Port
CHILD: Topology/IPClassA/Device = 2/Port/ifPhysAddress
CHILD: Topology/IPClassA/Device = 2/Port/poll_interval
CHILD: Topology/IPClassC
CHILD: Topology/IPClassC/Device
CHILD: Topology/IPClassC/Device/poll_interval
CHILD: Location
[download]

D:\Downloads>perl -w tmp.pl
Use of uninitialized value in quotemeta at tmp.pl line 9, <DATA> line 
+1.
CHILD: Topology/IPClassA/Device/log_ratio
CHILD: Topology/IPClassA/Device/poll_interval
CHILD: Topology/IPClassA/Device = 2/poll_interval
CHILD: Topology/IPClassA/Device = 2/is_managed
CHILD: Topology/IPClassA/Device = 2/Port/ifPhysAddress
CHILD: Topology/IPClassA/Device = 2/Port/poll_interval
CHILD: Topology/IPClassC/Device/poll_interval
CHILD: Location
[download]

This is one line less than what you want, as you seem to want to handle

CHILD: Topology/IPClassA/Device = 2/Port
[download]

perl -MHTTP::Daemon -MHTTP::Response -MLWP::Simple -e ' ;    # The  
$d = new HTTP::Daemon and fork and getprint $d->url and exit;#spider
($c = $d->accept())->get_request(); $c->send_response( new   #in the
HTTP::Response(200,$_,$_,qq(Just another Perl hacker\n))); ' #  web
[download]