1Should cvcache be per CV (keyed by thread) or per thread (keyed by CV)?
2
3Maybe ought to protect all SVs by a mutex for SvREFCNT_{dec,inc},
4upgrades and so on. Then use SvMUTEX instead of CvMUTEX for CVs.
5On the other hand, people shouldn't expect concurrent operations
6on non-lexicals to be safe anyway.
7
8Probably don't need to bother keeping track of CvOWNER on clones.
9
10Either @_ needs to be made lexical or other arrangments need to be
11made so that some globs (or just *_) are per-thread.
12
13tokenbuf and buf probably ought to be global protected by a global lock.
14