This wasn't so much about filtering the content, but instead having a list of dictionaries and filtering to ones with specific data.

auto data = [["key": 5], ["key": 2]];

auto foo = data.filter!(x => x["key"] == 5);

Well I showed this with my count example, it is one of the reasons I like D. I just keep with the same tools and there is similarities in how they all work. One of the challenges can be producing the ability to traverse, let me dive into this dictionary filtering.

import std.array;

auto dict = ["one" : 1
           , "two" : 2
           , "three" : 3];

dict.byPair
    .filter!(x => x[0] == "one")
    .assocArray;

In this case I'm asking to traverse the dictionary by each key/value pair. After the filtering we build out a new dictionary.

As an aside, while I find consistency in these, I'm also aware D has inconsistency.