Use the Super Mario Bros. 3 1-3 secret exit to get a Warp Whistle!

Mario crouches on the White Block for a few seconds to pass behind the scenery and use the World 1-3 Secret Exit to enter Toad's hidden Mushroom house and get the first Super Mario Bros. 3 Warp Whistle! Toad makes the instructions for use pretty clear, even though it leaves a little to interpretation. Still though, a Warp Whistle is a really handy thing! Best to carefully handle it and not accidentally use it!