open my $pipe, "traceroute ... |" or die;
my $start = time;
my $buf = '';
while(1) {
  my $vin = '';
  vec($vin, fileno($pipe), 1) = 1;
  if (select($vin, undef, undef, 1)) {
    sysread $pipe, $buf, 2048, length $buf
      or last;
  }
  last if time - $start > $timeout;
}
close $pipe;
# traceroute output is in $buf now