Added Kernel.then?/3 with a predicate parameter.

lib/elixir/lib/kernel.ex

@@ -2654,7 +2654,7 @@ defmodule Kernel do
   Pipes the first argument, `value`, into the second argument, a function `fun`,
   and returns the result of calling `fun`.
 
-  In other words, it invokes the function `fun` with `value` as argument,
+  In other words, it invokes the function `fun` with `value` as the argument,
   and returns its result.
 
   This is most commonly used in pipelines, using the `|>/2` operator, allowing you
@@ -2675,6 +2675,27 @@ defmodule Kernel do
     end
   end
 
+  @doc """
+  Pipes `value` into the given `fun` when `predicate` is truthy.
+
+  When the `predicate` is truthy `fun` will be called with `value`,
+  otherwise `value` is returned as is.
+  This is most commonly used in pipelines, allowing you
+  to pipe a value to a function outside of its first argument.
+
+  ### Examples
+
+      iex> opts = [flag: true]
+      iex> 1 |> then?(opts[:flag], & &1 + 10)
+      11
+  """
+  @doc since: "1.12.0"
+  defmacro then?(value, predicate, fun) do
+    quote bind_quoted: [value: value, predicate: predicate, fun: fun] do
+      if predicate, do: fun.(value), else: value
+    end
+  end
+
   @doc """
   Gets a value from a nested structure.