Grep like CLI that utilizes structural regular expressions. They should feel familiar to Kakoune (and Vis) users.
Let’s see an example: given a markdown file, list all headers, but ignore # in code blocks.
Kakoune filter:
kak -f 's```.+?```<ret>d%<a-s><a-K>^#+ <ret>d' < input
sregx
sregx "x/(?s)```.*?```/d | x/.*\n/ g/^#+\s(.+)/p" < input
The commands map almost 1:1. Pretty interesting.