xslt.pl:

#!/usr/bin/perl

use strict;
use warnings;

use XML::LibXML;
use XML::LibXSLT;

my $parser = XML::LibXML->new();
my $xslt = XML::LibXSLT->new();
  
my $source = $parser->parse_file('tmp.xml');
my $style_doc = $parser->parse_string(<<EOT);
<?xml version='1.0'?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0">
<xsl:strip-space elements="*"/>
<xsl:output method="xml" indent="yes"/>

    <xsl:template match="@* | node()">
        <xsl:copy>
            <xsl:apply-templates select="@* | node()" />
        </xsl:copy>
    </xsl:template>
   
    <xsl:template match="comment()" />
   
</xsl:stylesheet> 
EOT
  
my $stylesheet = $xslt->parse_stylesheet($style_doc);
  
my $results = $stylesheet->transform($source);
  
print $stylesheet->output_string($results);
----------------------------------------------
twig.pl:
#!/usr/bin/perl

use strict;
use warnings;

use XML::Twig;

my $twig = XML::Twig->new (comments => 'drop', pretty_print => 'indented');

$twig->parsefile("tmp.xml");
$twig->print();
----------------------------------
expat.pl:

#!/usr/bin/perl

use strict;
use warnings;


use XML::Parser::Expat;

my $parser = new XML::Parser::Expat;
$parser->setHandlers('Start' => \&sh,
                     'End'   => \&eh,
                     'Char'  => \&ch);
$parser->parsefile('tmp.xml');
sub sh {
  my ($p, $e) = @_;
  print $p->recognized_string();
}

sub eh {
  my ($p, $e) = @_;
  print $p->recognized_string();
}

sub ch {
  my ($p, $s) = @_;
  print $s;
}