use IO::Socket;
use XML::Simple;

my $cTelemetry = IO::Socket::INET->new( 'localhost:12345' ) or die $!;
my $cWaypoints = IO::Socket::INET->new( 'localhost:6789'  ) or die $!;

while( <cTelemetry> ) {
    my $xmlTelemetry = XMLin( $_ );
    if( my $xmlWaypoint = deriveWaypoint( $xmlTelemetry ) ){
         print $cWaypoints $xmlTelemetry;
    }
}