#!/usr/bin/perl

use strict;
use warnings;

use XML::Twig;

XML::Twig->new( start_tag_handlers => { _all_ => sub { my $tag= $_->tag; $tag=~ s{^[^:]*:}{}; $_->set_tag( $tag); } },
                                       keep_spaces => 1, # to keep formating
              )
         ->parse( \*DATA)
         ->print;

__DATA__
<a:houses>
    <a:house>
        <a:sq_footage/>
        <a:address/>
    </a:house>
    <a:house>
        <a:sq_footage/>
        <a:address/>
    </a:house>
</a:houses>