Perhaps something like

my $some_host = ...
my $pid = open TRACE, "traceroute $some_host |";

while (<TRACE>) {
  if (/some string/)  {
    close TRACE;
    kill 15, $pid;
    last;
  }

  # other processing here
}

# rest of script here
}
[download]

To handle the timeout you could use alarm, or non-blocking IO on TRACE and count seconds yourself.