Question about fast switch hash key-value pairs.

lihao has asked for the wisdom of the Perl Monks concerning the following question:

Hi, monks

Without loading any Perl modules, what is the fastest or best way to change key=>value pairs to value=>key pairs of a large hash. Assume no duplication in both key and value fields.. Many thanks

BTW. I am now using the following which looks dummy

  $hash1{$hash2{$_}} = $_ for keys %hash2;
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lihao

Comment on Question about fast switch hash key-value pairs. Download Code

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Re: Question about fast switch hash key-value pairs. by ikegami (Patriarch) on Apr 02, 2008 at 22:48 UTC
Your code is fine. Another way is to use a hash slice, using `values` to get the keys and `keys` to get the values. Yet another way is to assign one hash to the other while using `reverse`. All of these methods assumes the values are unique. Update: Added last solution.	[reply] [d/l] [select]
Re^2: Question about fast switch hash key-value pairs. by Erez (Priest) on Apr 03, 2008 at 06:46 UTC
All of these methods assumes the values are unique. You might want to add an `if exists` check in case the values are not unique, and perhaps add the duplicate values to an anonymous inner array (see HASHES OF ARRAYS). Software speaks in tongues of man. Stop saying 'script'. Stop saying 'line-noise'. We have nothing to lose but our metaphors.	[reply] [d/l]
Re: Question about fast switch hash key-value pairs. by FunkyMonk (Bishop) on Apr 02, 2008 at 21:32 UTC
Homework? Did you check the FAQ?	[reply] [d/l] [select]