With a name like that it wouldn’t 
and into %{} diverts attention from Map.new/1.
iex(1)> i = %{a: "hello", b: "world"}
%{a: "hello", b: "world"}
iex(2)> o = Map.new(i, fn ({k,v}) -> {k,String.upcase(v)} end)
%{a: "HELLO", b: "WORLD"}
iex(3)>
peerreynders
1