use warnings;
use strict;
use XML::Simple;
my $xml = XML::Simple->new(ForceArray => 1);
my $xml_Load = $xml->XMLin("Input.xml");
$xml->XMLout($xml_Load,OutputFile => "Output.xml");

# Here is the Output.xml file:

__END__

<opt>
  <global>
    <glob1 value="g1v" />
    <glob2 value="g2v" />
    <glob3 value="g3v" />
  </global>
  <parmsets>
    <example>
      <local>
        <loc2 value="loc2v" />
        <loc3 value="loc3v" />
        <location value="location" />
      </local>
      <regional>
        <region1 value="region1v" />
        <region2 value="region2v" />
        <region3 value="region3v" />
      </regional>
    </example>
  </parmsets>
</opt>