Imagine the case when an array holding key/value pairs is assigned to an hash (i.e. normal hash initialization). What exactly happens when the key gets repeated, i.e. is twice or more times inside the array (on odd positions of course)? Of course this is like assigning this hash key twice, e.g. the second assignment simple overwrites the first.
my @array = ( 'A', 1, 'B', 2, 'C', 3, 'A', 4 );
my %hash = @array;

# $hash{A} == 4 or 1 or depends??

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Now my actual question: Is this a defined, stable thing, e.g. always the last key in the array would win? Or is it - for any reason - the first? Is it not explicitly defined and depends on something like the internal hash structure, e.g. the exact key names?

I came to this question when I had code where I have to add certain key/value pairs to an existing hash and want to make sure that already existing keys are overwritten: 

%hash = (%hash,@array);
# or
%hash = (%hash,%otherhash);

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of course I could just take a loop for this but I like the simplicity of this line and because the existing hash isn't very big the reassigning to itself is not very expensive. Now I would like to know if this really works like I think it does.

In reply to Assigning list with duplicate keys to hash by mscharrer

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