my $counter = 0;
my $start;
my $end;
while (<DATA>) {
   $counter++ if /send/i;
   $start = time if($counter == 1);
   if($counter == 3){
     $counter = 0;
     $end = time;
     system("shellscript.sh &") if(($end - $start) > 3);
   }
}