gistfile1.js

 function concat() {
    var array = slice.call(this, 0), item;
    for (var i = 0, length = arguments.length; i < length; i++) {
      item = arguments[i];
      if (Object.isArray(item) && !('callee' in item)) {
        for (var j = 0, arrayLength = item.length; j < arrayLength; j++) 
          array.push(item[j]);
      } else { 
        array.push(item);
      }
    }
    return array;
  }
  // fix for opera
  var CONCAT_ARGUMENTS_BUGGY = (function() {
    return [].concat(arguments)[0][0] !== 1;
  })(1,2)
  
  if (CONCAT_ARGUMENTS_BUGGY) arrayProto.concat = concat;