These simple list-building instructions form the foundation of recursions, higher-order functions, and even higher-order abstractions like closures and continuations.
这些由列表构建的简单指令构成了递归、高阶函数，甚至是闭包和continuation之类高级抽象的基础。
You can store any Ruby object, even procs, lambdas, threads, continuations.
你可以保存任何Ruby对象，即使是proc、lambda、线程或者continuation。
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