在Perl 5中获得开关/案例的行为 [英] Obtain a switch/case behaviour in Perl 5

问题描述

在Perl 5中是否有一种巧妙的方式来进行案例或switch语句?在我看来，他们应该在版本6上添加一个开关.

Is there a neat way of making a case or switch statement in Perl 5?. It seems to me they should include a switch on version 6..

我需要在脚本中使用此控制结构，并且听说您可以导入开关模块".但是，如何在没有导入的情况下实现此目标，以最大程度地减少依赖关系并获得可移植性?

I need this control structure in a script, and I've heard you can import a "switch module". But how can I achieve it without imports to minimize dependencies and acquire portability?

推荐答案

如果您使用的是Perl 5.10，则具有 given/when 这是一个switch语句(请注意，它不仅可以与正则表达式进行比较，还可以阅读链接的文档以了解其全部潜能):

If you are using Perl 5.10 you have given/when which is a switch statement (note, it can do more than compare with regexes, read the linked docs to see its full potential):

#or any of the dozen other ways to tell 5.10 to use its new features
use feature qw/switch/; 

given($string) {
    when (/^abc/) { $abc     = 1; }
    when (/^def/) { $def     = 1; }
    when (/^xyz/) { $xyz     = 1; }
    default       { $nothing = 1; }
}

如果您使用的是Perl 5.8或更早版本，则必须使用if/elsif/else语句:

If you are using Perl 5.8 or earlier you must make do with if/elsif/else statements:

if    ($string =~ /^abc/) { $abc     = 1; }
elsif ($string =~ /^def/) { $def     = 1; }
elsif ($string =~ /^zyz/) { $xyz     = 1; }
else                      { $nothing = 1; }

或嵌套的条件运算符(?:):

$string =~ /^abc/ ? $abc     = 1  :
$string =~ /^def/ ? $def     = 1  :
$string =~ /^xyz/ ? $xyz     = 1  :
                    $nothing = 1;

Core Perl中有一个模块( Switch )，该模块通过源过滤器，但据我了解，它是

There is a module in Core Perl (Switch) that gives you fake switch statements via source filters, but it is my understanding that it is fragile:

use Switch;

switch ($string) {
    case /^abc/ {
    case /^abc/ { $abc     = 1 }
    case /^def/ { $def     = 1 }
    case /^xyz/ { $xyz     = 1 } 
    else        { $nothing = 1 }
}

或其他语法

use Switch 'Perl6';

given ($string) {  
    when /^abc/ { $abc     = 1; }
    when /^def/ { $def     = 1; }
    when /^xyz/ { $xyz     = 1; }
    default     { $nothing = 1; }
}

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