The lines t.xml = and -- end t.xml are not in the file t.xml; they were meant to show on screen where the file started and ended.

I modified your XML data because XML::Fast does not recognize it as XML with a tag and value, or tag, attribute, and value.

#!/usr/bin/env perl

use strict;
use warnings;

use XML::Fast;
use Data::Dumper;

my $xml = '<house_number>12</house_number>';
my $xml_hash = xml2hash $xml;
print Dumper($xml_hash),$/;

$xml = '<house number="12"/>';
$xml_hash = xml2hash $xml;
print Dumper($xml_hash),$/;

$xml = '<house_number="128"/>';
$xml_hash = xml2hash $xml;
print Dumper($xml_hash),$/;
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$VAR1 = {
          'house_number' => '12'
        };

$VAR1 = {
          'house' => {
                       '-number' => '12'
                     }
        };

$VAR1 = {
          'house_number="128"' => ''
        };
[download]

If you must use the XMLdata as given, i.e. <house_number="128"/> you'll probably end up having to write your own parser.