Add doctest example for broadcast!

base/broadcast.jl

@@ -713,6 +713,30 @@ Like [`broadcast`](@ref), but store the result of
 Note that `dest` is only used to store the result, and does not supply
 arguments to `f` unless it is also listed in the `As`,
 as in `broadcast!(f, A, A, B)` to perform `A[:] = broadcast(f, A, B)`.
+
+# Examples
+```jldoctest
+julia> A = [1.0; 0.0]; B = [0.0; 0.0];
+
+julia> broadcast!(+, B, A, (0, -2.0));
+
+julia> B
+2-element Array{Float64,1}:
+  1.0
+ -2.0
+
+julia> A
+2-element Array{Float64,1}:
+ 1.0
+ 0.0
+
+julia> broadcast!(+, A, A, (0, -2.0));
+
+julia> A
+2-element Array{Float64,1}:
+  1.0
+ -2.0
+```
 """
 broadcast!(f::Tf, dest, As::Vararg{Any,N}) where {Tf,N} = (materialize!(dest, broadcasted(f, As...)); dest)