Skew a Quad's Texture with UV instead of Vertices

Skew Quad by Brandon J. Matthews is a very useful script for giving Perspective Effects on Quads. However I wanted to ask how I can make it so that I’m directly skewing/distorting the Quad’s Texture with UV instead of with Vertices, keeping a Square/Rectangle Shape.

Otherwise, is there a way to put the skew/distorted mesh inside another mesh like a Sprite or Image Masking so that I can keep it in a Square/Rectangle Shape?