Question

我是perl的新手，正在尝试使用简单开关的代码。学校服务器只运行Perl 5.12.4，所以我正在编码。

我遇到的问题是，控制开关的变量不会抛出任何情况，无论我如何描述它们，并且总是会陷入默认情况。

忽略每个案例开关的内容，我只是试图让它至少抛出print命令，所以我知道开关正在运行。

# I have tried: case "1", case 1, case [1], case '1', and other variations.

#!/usr/bin/perl
# script name: phonebook.pl
while ( 1 ) {
print "Welcome to the Registry Searcher!\n";
print "Please enter a command matching one of the options below.\n";
print "1) List records alphabetically\n";
print "2) List records reverse alphabetically\n";
print "3) Search the Registry by Name\n";
print "4) Search the Registry by Birthday\n";
print "5) Exit\n";
print "Choice: ";
$in = <>;
    # user enters "1".
use Switch;
switch ($in) {
    case 1 {
        print "Please choose either first or last name (f/l): ";
        $type = <>;
        if ( $type == f ) {
            sort list.txt;
        } elsif ( $type == "l" ) {
            sort -k2 list.txt;
        } else {
            print "Choice not recognized.\n";
        }
        print "Please press enter to continue...";
        $cont = <>;
    }
    case 2 {
        print "Please choose either first or last name (f/l): ";
        $type = <>;
        if ( $type == "f" ) {
            sort -r list.txt
        } elsif ( $type == "l" ) {
            sort -rk2 list.txt
        } else {
            print "Choice not recognized.\n";
        }
        print "Please press enter to continue...";
        $cont = <>;
    }
    case 3 {
        print "Please enter a last name to search for: ";
        $name = <>;
        # awk '/^[A-Z][a-z]+ '$name'/{print}' list.txt;
        print "Please press enter to continue...";
        $cont = <>;
    }
    else {
    print "not found\n";
    }
}
}

Answer 1

您必须在chomp($in);之前添加switch以删除换行符。

<>读取流中的一行并包含换行符，其行为与类似scanf的函数不同。

Answer 2

你真的不想使用Switch;这是一个非常古老的源过滤器模块，它不可靠，并且无论如何很久以前就从Perl中删除了。

对于更好的现代替代方案，请参阅Switch::Plain或given/when内置运算符，但请注意后者的“实验”警告行为。

Perl 5.12.4，Switch无法正常工作？

2 个答案: