Joe Eli McIlvain

I've updated the PR to clear the `$ENV` value and `env` builtin, including tests and documentation changes to match. Thanks for the feedback! Let me know if there is anything...

I've pushed an amended commit that fixes the copy/paste mistake in the test echo strings noticed by @emanuele6. Regarding `input_filename` and `input_line_number`: There's possibly an argument for saying that `input_filename`...

@itchyny @wader @emanuele6 - can any of you give this PR a deeper review and approve it (or give further comments on things to be improved)?

If there's a fear that `--sandbox` "implies too much" about the security properties of the feature, or otherwise create confusion, I could rename it to more specifically pinpoint what it...

> A related thought is that, since there are so many different considerations and criteria regarding "security" and "sandbox", the "sandbox" flag could refer to a JSON object that specifies...

It's been about 6 months, so I'm checking in again. Any authoritative maintainer available to give direction on what changes are needed to get this across the finish line?

If my PR for the `--sandbox` flag (#3092) is merged first, then this PR should also be updated so that these new filesystem features are blocked by the `--sandbox` flag.

We agreed on the sync call to close this ticket for now, because it isn't reproducible anymore. If it starts happening again later, we can reopen this ticket.

Note that in the case where the return value of the iterator is a tuple, we should probably support some extra tuple destructuring on the left side: ``` pony for...

This feature would take care of the most immediate use case, perhaps, but I can still imagine wanting to pass a zipped iterator to another actor, for example. I think...