本文讨论一种非正则的评价函数和它的最优化的一种准则，给出在这种准则下构造按字典次序的最优二元树的一种算法。
The paper discusses a nonregular cost function and its optimum criterion, presenting an algorithm of constructing and optimal alphabetic binary tree under this criterion.
请注意，上面的正则表达式如何只捕获“connection from”和一个非数字的字符串后面的数字和点。
Note how the regular expression above captures only digits and dots, after "connection from" and a string of non-digits.
Perl 5提供了非内置的解析工具，但是它没有通过正则表达式提供词法分析工具。
Perl 5 offers no built-in parsing facilities, but it does offer lexing facilities through regular expressions.
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