There is a difference between "memory in use by the program" and, "memory claimed by perl from the OS, and not returned". When the program is run, the program needs memory, which is claimed from a pool managed by perl (the binary). If the pool gets empty, perl will claim more memory from the OS. If the program memory is reclaimed by the garbage collector (ref counting in the case of perl5), memory *may* be returned to the pool, or it may be kept around if perl thinks it might be reused. Perl might also return memory to the OS, but it's OS dependent whether that happens at all, and it's certainly not true that whenever the program no longer needs a piece of memory, it's returned to the OS.

If you really need this kind of memory management, you're probably better off programming in C.

Abigail