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Mastering Modern Perl: Writing Efficient and Maintainable Code

Manipulating Function Arguments

Learn how to manipulate function arguments.

We'll cover the following...

Flattening

List flattening into @_ happens on the caller side of a function call. Passing a hash as an argument produces a list of key/value pairs:

Perl
my %pet_names_and_types = (
    Lucky => 'dog',
    Rodney => 'dog',
    Tuxedo => 'cat',
    Petunia => 'cat',
    Rosie => 'dog',
);
show_pets( %pet_names_and_types );
sub show_pets {
    my %pets = @_;
    while (my ($name, $type) = each %pets) {
        say "$name is a $type";
    }
}

When Perl flattens %pet_names_and_types into a list, the order of the key/value pairs from the hash will vary, but the list will always contain a key, immediately followed by its value. Hash assignment inside show_pets() works the same way as ...