# read everything from the pipe.
my $pipename = "sensor-fifo";
while (1) {
    chomp(my $sensor = `cat $pipename`);
    my @args = split / /,$sensor;
    # 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 $f==0) { # I'm a child
        exec ("${perlhome}/upgrade-sensor.pl", @args)
      } 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";

}