use warnings;
use 5.014;  # for s///r
use File::Replace qw/replace3/;
use utf8;

my $mainkml = 'main.kml';
my $dynkml = 'dyn.kml';

open my $fh1, '>:encoding(UTF-8)', $mainkml or die "$mainkml: $!";
print $fh1 <<'END_KML1' =~ s/__FILENAME__/$dynkml/r;
<?xml version="1.0" encoding="UTF-8"?>
<kml xmlns="http://www.opengis.net/kml/2.2">
	<Folder>
		<name>Network Links</name>
		<visibility>0</visibility>
		<open>0</open>
		<NetworkLink>
			<name>Random Placemark</name>
			<refreshVisibility>0</refreshVisibility>
			<visibility>1</visibility>
			<open>1</open>
			<flyToView>1</flyToView>
			<Link>
				<refreshInterval>2</refreshInterval>
				<refreshMode>onInterval</refreshMode>
				<href>__FILENAME__</href>
			</Link>
		</NetworkLink>
	</Folder>
</kml>
END_KML1
close $fh1;

print "Please open '$mainkml' in Google Earth\n";

my $run = 1;
$SIG{INT} = sub { $run=0 };
my ($lat,$lon) = (52.514509,13.350103);
while ($run) {
	my (undef,$outfh,$repl) = replace3($dynkml, ':encoding(UTF-8)');
	print $outfh <<'END_KML2' =~ s/__LONLAT__/sprintf('%.6f,%.6f',$lon,$lat)/er;
<?xml version="1.0" encoding="UTF-8"?>
<kml xmlns="http://www.opengis.net/kml/2.2">
	<Placemark>
		<name>Random Placemark</name>
		<description>Hello, World!</description>
		<Point>
			<coordinates>__LONLAT__</coordinates>
		</Point>
	</Placemark>
</kml>
END_KML2
	$repl->finish;
	sleep 1;
	$lat += (rand(2)-1)/1000;
	$lon += (rand(2)-1)/1000;
}