while (my $host = pop @arrayofhosts) {    # $host is no longer in the array
  defined (my $pid = fork) or die "Cannot fork: $!";  # self-explanatory
  unless ($pid) {         
    # only the child will execute this code from here ...
         # do some things with $host
    exit 0; # very important!!! don't let it get past here
    # to here. At this point, the child process will terminate ...
  }

    # The parent continues here after forking the child
    # here it can do what it wants. 
    # you can rest here a while so you don't have too many zombies

    sleep (10);
    # now do some more things before forking the next child process

}