It should execute the block only if the passed in value is true, and return the conditional. Caller can optionally pass a value to be yield

yield_if.rb

def yield_if?(bool = false, value = nil)
  yield(value) if bool && block_given?
  bool
end

Too many times I end up writing code that looks like this

def foo
  ret = some_expensive_call
  do_something if ret
  ret
end

or
def foo
if ret = some_expensive_call
do_something
end
ret
end

What I want is:

def foo
  yield_if?(some_expensive_call) do
    do_something
  end
end

I could do this:

def foo
  returning( some_expensive_call, &lambda{ |boolean| do_something if boolean } )
end

Although I am not sure about the name for it. I also wonder if it already exists.
It calls the block only if the conditional is true, but I want the result of the conditional.