When in doubt, check for exceptions...

#!/usr/bin/perl -wT

use strict;
use Template;
use CGI;

my $q = CGI->new;
print $q->header("text/html");

my $template = Template->new( { INCLUDE_PATH => '/home/xxxx/yyy/zzzz' 
+} )
    || die Template->error(), "\n";
my $vars = { message => 'Hello', };
$template->process( 'test.html', $vars )
    || die $template->error();
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returns

Content-Type: text/html; charset=ISO-8859-1

file error - test.html: not found
[download]

Maybe you shoud just need to set your "INCLUDE_PATH" to the correct location of your test.html file?