I was refering to the fact that something on the C level is cached
without the Python user ever noticing that it wasn't there before.
Caching itself is no criteria, but allocating memory without giving the
user a chance to find out should be (in this context).
Maybe I am missing something here, but calling match.regs creates a
tuple which is not there before, but cannot be removed
afterwards. This is why I handled it separately.