That being said one way to see the Content-Range header would be to use %ENV to pull the 'HTTP_CONTENT_RANGE'.

print $ENV{HTTP_CONTENT_RANGE};
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Here is a test CGI script:

use warnings;
use strict;

use CGI;
use CGI::Carp qw(fatalsToBrowser);
use Data::Dumper;

my $q = CGI->new;
print $q->header,$q->start_html;
print '<pre>';
print Dumper \%ENV;
print '</pre>';
print "<br>Content-Range: ",$ENV{HTTP_CONTENT_RANGE};
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And a small fake request:

use warnings;
use strict;

use LWP::UserAgent;
my $ua = LWP::UserAgent->new;
my $req = HTTP::Request->new(GET => 'http://www.cicisdw.com/foo.cgi');
$req->header( 'Content-Range' => 'bytes 0-499/500' );
my $resp = $ua->request($req);
print  $resp->{_content};
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