gistfile1.js

$$('a[rel^="new_window"]').invoke('observe','click',function(evt){
  evt.stop();
  var opts = this.rel.split(',').invoke('strip');
  opts.shift(); //get rid of new_window 
  var name = 'popup';
  opts.each(function(opt,idx){
    var pair = opt.split(':').invoke('strip');
    if (pair[0] == 'name'){
      name = pair[1];
      delete opts[idx];
    }else{
      opts[idx] = pair.join('=');
    }
  });
  return window.open(this.href,name,opts.join(',') );
});