If you ever need to get unique values in Perl then you should think about using a hash.

use XML::XPath;

my $xp = XML::XPath->new(filename => '/path/to/file');

my %seen;
foreach ('IP-ADDRESS', 'IP-NEIGHBOUR') {
  foreach my $ip ($xp->findnodes("//$_")) {
    my $addr = $ip->findvalue('.');
    print "$addr\n" unless $seen{$addr}++;
  }
}

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<http://www.dave.org.uk>

"The first rule of Perl club is you do not talk about Perl club."
-- Chip Salzenberg

In reply to Re^2: Extracting tagged data from a XML file by davorg
in thread Extracting tagged data from a XML file by theroninwins

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