Actually Mac OS' Memory Manager is pretty apt at detecting low mem or mem2spare and can return it to the OS during runtime- of course, this has an effect on how one uses pointers, but it's not overly complicated. This is built into the Mac OS and is taken advantage of by MacPerl. Just a note!

Update: So it's true what everyone else says; you need to fork to actually be able to release memory back to the OS which is what Apache does in handling clients (which is configurable). Basically, the UN*X memory model is eat as much memory as allowable until crash or exit() (the max mem usage is configurable via hard and soft limits and compile-time options).

AgentM Systems nor Nasca Enterprises nor Bone::Easy nor Macperl is responsible for the comments made by AgentM. Remember, you can build any logical system with NOR.