Perl 5:

All the really good stuff nowadays seems to require mod_perl, which has low availability everywhere I want to go. Some really incredible functionality can be encapsulated in modules, but what is under the hood is often fragile or frightening: source filters, typeglobs, whatever Moose is doing... DateTime is brilliant but still made some very bad design decisions (not returning a stopwatch duration when subtracting two DateTime objects) Dual-lifed modules in core and on CPAN still cause conflicts module authors still put interactive stuff in their module configuration scripts so that they can't be automatically installed

C#

1)缺乏为值类型编写泛型的实际能力。例如，任何白痴(好吧，大多数白痴)都可以编写一个例程，用c++计算int, float, double等列表的标准偏差，它写起来很简单，易于阅读，并作为快速的非泛型代码执行。我认为，如果你能用c#写一些东西，接近于达到这三个中的任何一个，而在其他两个上又不荒谬，你就是一个真正伟大的程序员。

2)协方差和反方差，尽管这被添加到4。

3)非常糟糕的LINQ文档(好吧，并不是语言的一部分)。

4)尝试使用foreach/迭代器，当我每次都想做同样的事情，除了上次略有不同(如连接一串字符串与逗号之间的单词和最后两个)。如果我用一个IEnumerable来写它，它很难写和读，而用一个for (int I =0 I <…)它并没有好到哪里去，而且效率更低。

5)我知道我会收到抱怨，但是缺少受控的例外。这并不需要像在java中那样实现(框架开发人员确实提出了一些很好的观点，为什么他们没有这样做)，但我很乐意看到编译器警告不喜欢受控异常的用户可以关闭。

Haskell

Sometimes the type system feels backwards. What if I don't want the compiler to infer types for my variables? What if I want the opposite, where it does constraint checking on said variables? For example, instead of inferring the type of the elements of a list, it instead makes sure that they all belong to a particular typeclass. This is a subtle but huge difference that makes it difficult for me to program UIs. It can be done, but it takes more effort than it does in some other languages. Haskell rocks for the non-UI parts, but the UI I leave to an untyped language. Allowing the construction of infinite values leads to some really frustrating errors sometimes. NoMonomorphismRestriction. Bytestring handling bites me in the ass sometimes and you don't know it until your program crashes because you mixed them up improperly. Something is wrong here, when we are losing type information that should have prevented this. Typeclasses should be automatically derived for trivial cases, like witness types, but there's a strong potential for abuse there.

Ruby。

Strange scoping rules - variables, constants, and methods each behave differently from each other. The rules change also depending on which keyword you used to create a closure. Or on whether you're in a class, eigenclass, object, module, or module's self. Then there's instance_eval, which changes the rules to a different set of rules. And they change again when a module is "included" or "extended", which themselves do different things to scope. And some sets of rules can't be emulated by metaprogramming, so you have to use eval. Unless you're on ruby 1.9, where all of this is different. Namespacing is basically useless. If you have Foo::File, then the stdlib File is probably broken for all of Foo. require statement is broken. If two files require eachother, the behavior of those files can change dramatically depending on which is loaded first from elsewhere. libraries change APIs dramatically and suddenly, so you have to require specific minor revision numbers of all of your dependencies. For every single ruby application on your system. The rubygems package system overrides "require" rather than putting files in the search path - because why use a system when you can replace it?

Lua:

The built-in error system is absolutely horrendous You can implement a try-catch system by modifying the Lua interpreter; but it has no compatibility with the errors that are thrown by the built in functions. The fact they have __newindex instead of __setindex as the setter ... and __newindex is only fired when the key doesn't already exist. If it does, no metamethod is called at all. No good type comparison system. There's the type() function but it only handles the basic types (all tables are tables). It really needs to have a metamethod for type comparisons. I've implemented this before with an 'is' operator and a __type metamethod and it works really nicely. It's a bitch to define new keywords. You can do it, but the code inside Lua isn't well documented so it's kind of trial and error to find out how to get the result you want. This is a major issue when you want to implement the things I mentioned above yourself (not so much __setindex though, that's an easy modification). I can't use it in a web browser. Yeah not really a problem with the language itself, but damn, would I love to be able to use Lua instead of Javascript... :)

C#

我对c#非常满意，但这两个真的让我很恼火:

Constructor-based initialization for immutable classes is less convenient, less intuitive (when you read the code you don't understand what you assign to what), has less IDE backing than inline object initialization. This makes you lean towards mutable classes inevitably. I know this has been mentioned before, but I strictly have problems with initialization syntax for immutable classes. switch is too verbose. Whenever I see a situation where a switch would be proper, I'm really inclined to use an if..else if.. just because it's more terse (~30% less typing). I think there should be no fallthrough for switch, break should be implied, and case should allow comma separated list of values.