What are the characteristics of a namespace when Perl is in safe mode?

What will be an ideal response?

A new and separate namespace has the following characteristics:
* Each namespace runs in its own scope. The namespace is changed to locate in a different package, and code evaluated in the compartment cannot refer to variables outside its scope.
* The code outside the compartment has the option to share variables within the compartment's namespace. Only the shared data will be visible to code evaluated in the compartment.
* In order to allow Perl operators such as the ones default to $_, and assignment to @_ on subroutine entry to work, all "underscore" variables are shared within the compartments by default.