libdevel-refcount-perl binary package in Ubuntu Xenial amd64

 Devel::Refcount provides a single function which obtains the reference count
 of the object being pointed to by the passed reference value.
 .
 Internally, Perl maintains a count of the number of 'things' referring to each
 variable, as a means of providing automatic memory management. Every time a
 reference is made to a scalar value, for example, the reference count is
 incremented; every time that reference is lost (eg. when a lexical variable
 goes out of scope) then the reference count is decremented.

Source package