find(sub {
    return if !/\.ktf\z/;

    print("$File::Find::name\n");
    open(my $fh_in, '<', $File::Find::name)
        or die("Can't open file \"$File::Find::name\": $!\n");

    while (my $line = <$fh_in>) {
        next if $. <= 2;
        print $fh_out $line;
    }
}, '.');