Tried to do this a while ago and had the same fork/exec problem. It's possible to fork/exec and have the page load. Apache waits for the child process to close off its handles before loading. So you just have to close them manually:

  if (!defined( my $child_pid = fork()))
  { die "Cannot Fork: $!" }
  elsif ($child_pid)
  {
    print "</body></html>";
    exit(0);
  }
  else
  {
    close(STDOUT);  
    close(STDERR);
    close(STDIN);

    exec("$my_command");
    exit(0);
  }
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If you're planning on launching processes and don't really need a web interface, it's worth considering perl Tk. OK user interface, fewer security issues, and no quirks introduced by apache.