如何检查，如果值是在Perl列表？ [英] How can I check if a value is in a list in Perl?

问题描述

我有一个文件，其中的每一行是一个整数，再presents的ID。我想要做的就是检查一些特定的ID是否在此列表中。
但是，code没有工作。它从来没有告诉我它的存在，即使123在该文件中的一行。我不知道为什么？帮助AP preciated。

I have a file in which every line is an integer which represents an id. What I want to do is just check whether some specific ids are in this list. But the code didn't work. It never tells me it exists even if 123 is a line in that file. I don't know why? Help appreciated.

open (FILE, "list.txt") or die ("unable to open !");

    my @data=<FILE>;

    my %lookup  =map {chop($_) => undef} @data;

    my $element= '123';
    if (exists $lookup{$element})
    {
        print "Exists";
    }

先谢谢了。

推荐答案

用Perl 5.10及以上，您还可以使用智能匹配运算符：

With Perl 5.10 and up, you can also use the smart match operator:

my $id = get_id_to_check_for();
open my $fh, '<', 'list.txt' or die "unable to open list.txt: $!";
chomp( my @data = <$fh> );
print "Id found!" if $id ~~ @data;

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