You don't need the global variable (at least, the Scheme equivalent does not - I'm not going to lawyer over how variable capture would work in a hypothetical dialect of C++ that added call/cc). Any variable in scope to be captured by 'g' will do. There may be some misunderstanding in your statement "all local variables remain the same as they were before" - the same bindings will exist, but the values are not restored to their values prior to the call/cc, such that any subsequent changes to those variables will be preserved, permitting exactly the sort of thing you used as an example (albeit using a global variable).
You're right: there's lots of little mistakes I have in that post. And I think the variable binding vs variable-values thing is a major mistake I left in there... and I appreciate the corrections.
Hopefully my relatively low-effort translation is useful to someone out there. But yes, I do admit that I "err on the side of incorrect", trying to favor simplicity in the explanation instead.
