In Data.List from base 4.6.0.0 (as in every previous version), the documentation for insert says "The insert function takes an element and a list and inserts the element into the list at the last position where it is still less than or equal to the next element." However:

insert 1 [2,3,4,2,3,4]

[1,2,3,4,2,3,4]

One could correct the code to match the documentation. However, any maximally productive version is likely quite a bit less efficient than the current code, and the documented behavior doesn't seem terribly useful.

Instead, I suggest patching the documentation in the obvious way: "The insert function takes an element and a list and inserts the element into the list at the first position where it is less than or equal to the next element."