$ comrak
Hello ~world~ there.

Hello www.github.com.

* [x] Done
* [ ] Not done

****abcd****
$ comrak --gfm
Hello ~world~ there.

Hello www.github.com.

* [x] Done
* [ ] Not done

****abcd****
$ comrak
| a | b |
|---|---|
| c | d |
$ comrak --gfm
| a | b |
|---|---|
| c | d |