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Home: Perl Programming Help: Frequently Asked Questions:
How do I look up a hash element by value?

Jasmine
Administrator

Jan 19, 2001, 3:23 PM

Post #1 of 1 (3164 views)

How do I look up a hash element by value?	Can't Post

(From the Perl FAQ)

How do I look up a hash element by value?

Create a reverse hash:

Code

    %by_value = reverse %by_key; 
    $key = $by_value{$value};

That's not particularly efficient. It would be more space-efficient to use:

Code

    while (($key, $value) = each %by_key) { 
        $by_value{$value} = $key; 
    }

If your hash could have repeated values, the methods above will only find one of the associated keys. This may or may not worry you.

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