! Aware to Perl: How do I look up a hash element by value?

How do I look up a hash element by value?

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Create a reverse hash:

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

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

    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.

Source: Perl FAQ: Data Manipulation
Copyright: Copyright (c) 1997 Tom Christiansen and Nathan Torkington.

(Corrections, notes, and links courtesy of RocketAware.com)

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