use XML::Twig;
use strict;

my $xml = do {local $/; <DATA>};

my $twig = XML::Twig->new(
	keep_spaces => 1,
);
$twig->parse($xml);

foreach my $node ($twig->findnodes(q{//cidr-map-to[@name='AKA Edge']/blocks})) {
	$node->set_text(join ' ', reverse split ' ', $node->text());
}

$twig->print();

__DATA__
<root>
<cidr-map name="Internal test" default-datacenter="Default Datacenter">
<cidr-map-to name="AKA Edge">
<blocks>127.0.241.174 127.0.0.181</blocks>
</cidr-map-to>
</cidr-map>
<cidr-map name="Prod Internal Actual" default-datacenter="Default Datacenter">
<cidr-map-to name="AKA Edge">
<blocks>127.0.12.1 10.0.0.1 198.168.1.1</blocks>
</cidr-map-to>
</cidr-map>
</root>