defmodule X do
// I want to match if key1 is the ONLY key in the map
def match_only_map1(%{key1: _}), do: true
def match_only_map1(_), do: false
end
map1 = %{key1: 1}
map2 = %{key1: 1, key2: 2}
IO.inspect(X.match_only_map1(map1))
IO.inspect(X.match_only_map1(map2))