Problem

The keys and each functions give you the hash elements in a strange order, and you want them in the order in which you inserted them.

Solution

Use the Tie::IxHash module.

use Tie::IxHash; tie %HASH, "Tie::IxHash"; # manipulate %HASH @keys = keys %HASH;         # @keys is in insertion order

Discussion

Tie::IxHash makes keys , each , and values return the hash elements in the order they were added. This often removes the need to preprocess the hash keys with a complex sort comparison or maintain a distinct array containing the keys in the order they were inserted into the hash.

Tie::IxHash also provides an object-oriented interface to splice , push , pop , shift , unshift , keys , values , and delete , among others.

Here's an example, showing both keys and each :

# initialize use Tie::IxHash;  tie %food_color, "Tie::IxHash"; $food_color{Banana} = "Yellow"; $food_color{Apple}  = "Green"; $food_color{Lemon}  = "Yellow";  print "In insertion order, the foods are:\n"; foreach $food (keys %food_color) {     print "  $food\n"; }  print "Still in insertion order, the foods' colors are:\n"; while (( $food, $color ) = each %food_color ) {     print "$food is colored $color.\n"; }  



In insertion order, the foods are:



 



  Banana



 



  Apple



 



  Lemon



 



Still in insertion order, the foods' colors are:



 



Banana is colored Yellow.



 



Apple is colored Green.



 



Lemon is colored Yellow.

See Also

The documentation for the CPAN module Tie::IxHash; Recipe 13.15