And XML::Simple works

use strict;
use warnings;
use Data::Dumper;

use XML::Simple;

my $ref = XMLin('test.xml');

print Dumper($ref->{"env:Body"}->{"m:markupvalidationresponse"}->{"m:e
+rrors"}->{"m:errorlist"}->{"m:error"});
[download]

produces

$VAR1 = [
          {
            'm:line' => '11',
            'm:col' => '66',
            'm:message' => 'document type does not allow element "LINK
+" here'
          },
          {
            'm:line' => '14',
            'm:col' => '41',
            'm:message' => 'document type does not allow element "LINK
+" here'
          },
          {
            'm:line' => '21',
            'm:col' => '4',
            'm:message' => 'document type does not allow element "META
+" here'
          }
        ];
[download]