bless(\{hash => \{}}, $class);

That blesses a reference to a reference to a hash that contains a single value that is a reference to a reference of a hash.

The { } hashref construct creates a hash reference for you, so there is no need to put a backslash in front of it. That will only create a reference to the newly created reference to an anonymous hash.

Without the backslashes:

bless { hash => {} }, $class;
...
$object->{hash}->{key_inside_that};
[download]

The arrow between two sets of braces is optional, and it's not the only notation. Here are a few alternatives (less good, imho):

$object->{hash}{key_inside_that},
$$object{hash}{key_inside_that},
${${$object}{hash}}{key_inside_that}
[download]

If you don't remove the backslashes, you will have scalar references, and those can only be dereferenced with the ugly syntax:

bless \{ hash => \{} }, $class;
...
${$$object->{hash}}->{key_inside_that};
${${${$object}}{hash}}{key_inside_that};
# etcetera...
[download]

Read perlref for more information.

HTH

- Yes, I reinvent wheels.
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