Why <a-k> ; <a-K> don't work for me?

I need help to keep or clear parts of multible seletions.

For exsample I press
% s set-option
and get any selections [set-option] and all is OK.
But after
alt-k set-
it shall only stay [option] in my selections, but nothing happens.
The same behaviour with alt-K.
I had tested it without my kakrc and without system config.
Were is my misstake?
What is wrong?

Michael

The alt K combos filter entire selections while s selects things inside your current selection. So what you want to do is

sset-option<ret>soption<ret>
or instead using fancy regex
sset-\Koption<ret>

What you’re currently doing with <a-k> is filtering out all selections not containing option (which does nothing). <a-K> filters out selections containing option but that will fail with an error because it would leave you with no selections (which is forbidden).

Thank you prion,
I misunderstand K combos filter.
For complexer selections/regexes the K combos filter now work for me also.

Michael