code: public void runRunnableSubcommand(List<CommandLine> parsedCommands) throws Exception {
          CommandLine deepestSubcommand = parsedCommands.get(parsedCommands.size() - 1);
          Object commandObject = deepestSubcommand.getCommand();
          if (commandObject == this) {
              return;
          }
          if (commandObject instanceof Runnable) {
              ((Runnable) commandObject).run();
          } else if (commandObject instanceof Callable<?>) {
              ((Callable<?>) commandObject).call();
          }
      }
docs: If the most specific subcommand (the last {@code CommandLine} object in the list) implements Runnable or Callable,
  then run it.
  This method will not run the main script {@link #runScriptBody()} method; that will be called from {@code {@link #run()}}.
  
  @param parsedCommands the list of {@code CommandLine} objects returns from the {@code CommandLine.parse} method
  @throws Exception if the Callable throws an exception