#!/usr/bin/perl --

use strict;
use warnings;

use XML::Twig;
{
  my $xml = <<'__XML__';
<?xml version="1.0"?>
<TOP>
  <SUB>
    <THIS>STUFF</THIS>
    <SOME.TYPE>T</SOME.TYPE>
    <SOME.OTHER.TYPE>BLAH</SOME.OTHER.TYPE>
  </SUB>
</TOP>
__XML__

  my $t = XML::Twig->new(
    pretty_print  => 'indented',
    twig_handlers => {
      '_all_' => sub {
        my ( $t, $e ) = @_;
        my $tag = $e->tag;
        if ( $tag =~ s/\.//g ) {
          $e->set_tag($tag);
        }
        $t->flush;    ## does the printing
        return;
      },
    },
  );
  $t->xparse($xml);
  $t->purge;
  undef $t;
}

__END__
<?xml version="1.0"?>
<TOP>
  <SUB>
    <THIS>STUFF</THIS>
    <SOMETYPE>T</SOMETYPE>
    <SOMEOTHERTYPE>BLAH</SOMEOTHERTYPE>
  </SUB>
</TOP>