Copying values from one hash to another in perl

Question

I have two hashes, one big and one small. All of the smaller hash's keys show up in the bigger hash, but the values are different. I want to copy the values from the bigger hash to smaller hash.

E.G.:

# I have two hashes like so
%big_hash = (A => '1', B => '2', C => '3', D => '4', E => '5');
%small_hash = (A => '0', B => '0', C => '0');
# I want small_hash to get the values of big_hash like this
%small_hash = (A => '1', B => '2', C => '3');

An obvious answer would be to loop through the keys of the small hash, and copy over the values like this

foreach $key (keys %small_hash) { $small_hash{$key} = $big_hash{$key}; }

Is there a shorter way to do this?

Answer 1

@small_hash{ keys %small_hash } = @big_hash{ keys %small_hash };

Answer 2

Here's a way you could do it:

%small = map { $_, $big{$_} } keys %small;

Altho that's pretty similar to the for loop.

$small{$_} = $big{$_} for keys %small;

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map proof for those that need one:

my %big = (A => '1', B => '2', C => '3', D => '4', E => '5');
my %small = (A => '0', B => '0', C => '0');

%small = map { $_, $big{$_} } keys %small;

print join ', ', %small;

Output:

A, 1, C, 3, B, 2