This seems to do the job:

#!/usr/bin/env perl

use strict;
use warnings;
use XML::LibXML 2;

my $xml = "XML::LibXML"->load_xml(location => "input.xml");

for my $hg ($xml->findnodes('//host-group'))
{
    my $path = join ".", $hg->findnodes('ancestor-or-self::host-group'
+)->map(sub { $_->{name} });
    my @ips  = $hg->findnodes('ip-address-ranges')->map(sub { split /\
+s*,\s*/, $_->textContent });
    print "$path\t$_\n" for @ips;
}
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