Initial scratchings with a kris knife. The undulations seem to aid in slashing and piercing. The forward curves dig into the material and the widest part if the blade is close to the tip so once that's through there's very little resistance.

Kris blades seem to be esoteric due to their rarity and people claim absolute insanity when speculating about the use of the undulations. So I've always wanted to try one myself, if only it was convenient to do more extensive testing.