The Perl garbage collector uses simple reference counting during the normal
execution of a program. This means that cycles or unweakened references in
other parts of code can keep an object around for longer than intended. To
help avoid this problem, the reference count of a new object from its class
constructor ought to be 1. This way, the caller can know the object will be
properly DESTROYed when it drops all of its references to it.

Homepage:
https://metacpan.org/release/Test-Refcount
