Lua:

元表是如此令人困惑，直到他们“点击” 缺少像a += 20这样的赋值操作符是一种痛苦 没有集成的面向对象的解决方案意味着每个人和他的狗都使用自己的口味 用于注释(——)的语法排除了加/减前后操作符的可能性 不入侵C端就不可能有任何先发制人的多任务系统

Ruby:

重要的空白。对于解释器，行尾=语句的结束，除非看起来语句应该继续(或者显式转义换行符)。 慢 在线文档不如Python的好(为了辩护，Python的很棒) 我刚才提到慢了吗?

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.

Python:

Global Interpreter Lock - Dealing with this complicates parallel processing. Lambdas functions are a bit clunky. No built-in ordered-dictionary type. Depending on how Python is compiled, it can use either UCS-2 vs UCS-4 for the internal Unicode encoding, many string operators and iterators may have unexpected results for multi-byte characters that exceed the default width. String slicing and iteration depend on the bit width rather than checking and counting characters. (Most other programming languages do similar things as well and have similarly odd behavior with these characters.) There are inconsistencies surrounding GUI frameworks for Python.

c# / .net:

Classes should be sealed by default There should be no lock statement - instead, you should have specific locking objects, and there should be methods such as Acquire which return disposable lock tokens. Corollary: there shouldn't be a monitor for every object. GetHashCode() and Equals() shouldn't be in System.Object - not everything's suitable for hashing. Instead, have an IdentityComparer which does the same thing, and keep the IComparer<T>, IComparable<T>, IEqualityComparer<T> and IEquatable<T> interfaces for custom comparisons. Poor support for immutability Poor way of discovering extension methods - it should be a much more conscious decision than just the fact that I'm using a namespace.

这些都是我想出来的，明天问我，我会想出一个不同的5个:)

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