You can use XML::Rules and specify what tags do you want to keep as text. Something like this:

use strict;
use XML::Rules;
use Data::Dumper;

my $parser = XML::Rules->new(
    stripspaces => 2,
    rules => {
        '_default' => 'as array',
        'Publisher' => 'pass',
        'Emphasis' => sub {
            my ($tag,$attr,$parser) = @_[0,1,4];
            return $parser->ToXML($tag, $attr);
        }
    }
);

print Dumper($parser->parse(\*DATA));

__DATA__
<Publisher>
  <UniqueDOI>978-3-642-123456</UniqueDOI>
  <ChapterInfo ChapterType="OriginalPaper">
    <Title Language="En">Is Light Blue (<Emphasis Type="Italic">azzurr
+o</Emphasis> o bianco) Color Name Universal in the Italian Language?<
+/Title>
  </ChapterInfo>
</Publisher>
[download]

You can specify a comma separated list of tags in place of the 'Emphasis' and if some other tags are not allowed to repeat, you may include 'their,names' => 'as is' in the rules hash.