If you use Data::Dumper along with XML::Simple (the dynamic duo?) you can see that, using forcearray => 1 with XML::Simple, your XML becomes this:

$VAR1 = {
          'node' => {
                      'edge2' => {
                                   'community' => [
                                                    'anotherthing'
                                                  ],
                                   'loopback' => [
                                                   '10.6.21.10',
                                                   '10.12.71.14'
                                                 ]
                                 },
                      'edge1' => {
                                   'community' => [
                                                    'something'
                                                  ],
                                   'loopback' => [
                                                   '172.16.254.10'
                                                 ]
                                 }
                    }
        };
[download]

So, I believe you want something like this:

#! /usr/bin/perl

use strict ;
use warnings ;
use XML::Simple ;
#use Data::Dumper ;

my $xml = <<'EOD' ;
<network>
<node name="edge1">
<community>something</community>
<loopback>172.16.254.10</loopback>
</node>
<node name="edge2">
<community>anotherthing</community>
<loopback>10.6.21.10</loopback>
<loopback>10.12.71.14</loopback>
</node>
</network>
EOD

my $data = XMLin( $xml, forcearray => 1 ) ;
#print Dumper( $data ) ;

foreach my $key ( keys %{$data->{'node'}} )
{
    foreach my $loopback ( @{$data->{'node'}{$key}{'loopback'}} )
    {
        print "key = $key; loopback = $loopback\n" ;
    }
}
[download]

Output:

key = edge2; loopback = 10.6.21.10
key = edge2; loopback = 10.12.71.14
key = edge1; loopback = 172.16.254.10
[download]