static class LHotwire extends LearnerImpl {
  static boolean cacheSnippets = true;
  static new (Tree)Map<Long, Class> cache;
  
  static boolean debug;
  String programID;
  Class prog;

  *(String *programID) {}
  
  public void processInOut(Object in, Object out) {
  }
  
  public Object processIn(Object in) {
    if (prog == null) {
      prog = cache.get(parseSnippetID(programID));
      if (prog == null) {
        if (debug)
          debug("Loading " + programID);
        prog = hotwire(programID);
        if (cacheSnippets)
          cache.put(parseSnippetID(programID), prog);
      }
    }
    
    set(prog, "in", in);
    call(prog, "main", new Object[] {new String[0]});
    in = get(prog, "in");
    if (debug)
      debug(programID + " returned: " + structure(in));
    return in;
  }
}

Began life as a copy of #1000532