Perl doesn't have "garbage collection" in the sense that it never gives memory back to the OS
Sorry, but that statement is garbage.
First, the statement is wrong, as already demonstrated by BrowserUk.
Whether perl releases memory back to the OS or not
depends simply on the implementation of
as described at Re: Not able to release memory.
Second, whether it returns memory to OS is not related to garbage collection!
As already noted by dave_the_m, perl uses a reference-counted garbage
collector, so you get "deterministic destructors" for free
(i.e. in perl, you are guaranteed that an object is destroyed (and destructor called) immediately its reference count goes to zero).
BTW, deterministic destructors are a feature of the C++ RAII idiom
yet are problematic when using a mark-and-sweep garbage collector,
such as that used by Java, which is why Java has a "finally" clause
(see also Dispose pattern).