How can I create a nested hash as a constant in Perl?

Question

I want to do, in Perl, the equivalent of the following Ruby code:

class Foo
  MY_CONST = {
    'foo' => 'bar',
    'baz' => {
      'innerbar' => 'bleh'
    },
  }

  def some_method
    a = MY_CONST[ 'foo' ]
  end

end

# In some other file which uses Foo...

b = Foo::MY_CONST[ 'baz' ][ 'innerbar' ]

That is, I just want to declare a constant, nested hash structure for use both in the class and outside. How to?

Answer 1

You can also do this entirely with builtins:

package Foo;
use constant MY_CONST =>
{
    'foo' => 'bar',
    'baz' => {
        'innerbar' => 'bleh',
    },
};

sub some_method
{
    # presumably $a is defined somewhere else...
    # or perhaps you mean to dereference a parameter passed in?
    # in that case, use ${$_[0]} = MY_CONST->{foo} and call some_method(\$var);
    $a = MY_CONST->{foo};
}

package Main;  # or any other namespace that isn't Foo...
# ...
my $b = Foo->MY_CONST->{baz}{innerbar};