[feature request] Support looping over simple lists

Historically, looping has been pretty handy. Simple support is wanted to avoid lengthier JavaScripts:

```sh
$ for i in a b c; do echo 1 $i 2; done
1 a 2
1 b 2
1 c 2
```

The intended use case is simple lists and differs from `xargs` which is useful for mapping stdin to a command.

## References
- [Split from similar xargs -I issue](https://github.com/denoland/deno_task_shell/issues/77)