# read everything from the pipe.
my $pipename = "sensor-fifo";
while (1) {
    chomp(my $sensor = `cat $pipename`);
    # Something in pipe; see if it is real or just empty string
    # [Omitted more sophisticated tests here]
    if ($sensor) {
      print "upgrade requested for $sensor, forking...\n";
      my $f=fork;
      if(defined ($f) and $f==0) { # I'm a child
          # Here you can the shell meta-characters 
          my $result = system("${perlhome}/upgrade-sensor.pl $sensor >> ${workpath}/worklog 2>&1");
          # System is a blocking call, meaning that the 
          # intermediate process does not exit.
          print "result for $sensor was $result.\n";
          exit(0);
      } elsif (defined ($f)==0) { # Fork failed
        print "Fork failed for $sensor!\n";
      }
      # else I'm the parent
    }
    print "waiting on child $$ to complete $sensor.\n";
    1 while waitpid(-1, WNOHANG)>0; # reaps children
    print "Finished waiting.\n";

}