for (split //, $template) {
    print ord == 0 ? '.' : 'X';
}
print "\n";
[download]

Another way to do that:

$template =~ tr/\0/X/c;
$template =~ tr/\0/./;
print "$template\n";
[download]

But this looks like it produces the output the OP wants:

print "position $-[0] is not conserved\n" while $template =~ /[^\0]/g;
[download]