keys $blessed doesn't work for a very good reason. keys can (in recent versions of Perl) be used with either arrays or hashes. A blessed object can (thanks to overload) be simultaneously dereferencable as a hash and and array. So for blessed objects, you need to manually dereference.
Sure, those work fine, but aren't really new work, just syntactic sugar over $x = defined($x) ? $x : $value, a local $\ = "\n" (and print), and a function closed over a variable declared in an outer lexical scope (this is actually superior to the sugar, since you can have multiple functions sharing the same variable).