> Why so coarse?

> Getting a notification for every change of a global in module, is likely to make use the use of global variables extremely expensive.

Perhaps a compromise is possible here: one global group/chain of callbacks registered for all dictionaries in an interpreter seems reasonable (to keep overhead low), but we could reduce the number of times it’s actually called by, say, tagging specific values of specific dictionaries to be watched.

For example, we could just tag the low bit of any pointer in a dictionary’s values that we want to be notified of changes to. Something like that seems like it could really keep the cost of watching down without sacrificing power.