$hash = { 'Man' => 'Bill',
'Woman' => 'Mary,
'Dog' => 'Ben'
};
What exactly do Perl's “anonymous hashes” do?
It is a reference to a hash that can be stored in a scalar variable. It is exactly like a regular hash, except that the curly brackets {...}
creates a reference to a hash.
Note the usage of different parentheses in these examples:
%hash = ( foo => "bar" ); # regular hash
$hash = { foo => "bar" }; # reference to anonymous (unnamed) hash
$href = \%hash; # reference to named hash %hash
This is useful to be able to do, if you for example want to pass a hash as an argument to a subroutine:
foo(\%hash, $arg1, $arg2);
sub foo {
my ($hash, @args) = @_;
...
}
And it is a way to create a multilevel hash:
my %hash = ( foo => { bar => "baz" } ); # $hash{foo}{bar} is now "baz"