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Mastering Modern Perl: Writing Efficient and Maintainable Code

Hash Slices

Explore the concept of hash slices in Perl to efficiently manipulate multiple elements in hashes. Learn to initialize, retrieve, and merge hash values in a single operation, understand how hashes behave in different contexts, and manage key/value pairs effectively.

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Introduction to hash slices

A hash slice is a list of keys or values of a hash indexed in a single operation. Here’s how to initialize multiple elements of a hash at once:

Perl
my %cats;
@cats{qw( Jack Brad Mars Grumpy )} = (1) x 4;
 
# printing the hash
for (keys %cats) {
   say "$_ => $cats{$_}";
}

This is equivalent to the following initialization:

Perl
my %cats = map { $_ => 1 } qw( Jack Brad Mars Grumpy );
 
# printing the hash
for (keys %cats) {
  say "$_ => $cats{$_}";
}

Note: The hash slice assignment can also add to the existing contents of the hash.

Retrieving multiple values

Hash slices also allow us to retrieve multiple values from a hash in a single operation. As with array ...