if(my $pid=fork){
  #parent
  my $run = 1;
  $SIG{CHLD} = sub { 
    $deadchildpid = wait;
    $run = 0
  };
  my $count = 0;
  while($run){
     sleep(1);
     print $count++;
  }
}
else {
 #child
 while(my $c = ReadKey){
     #doing something... ;
  }
}