modified version of http://elm-lang.org/edit/examples/Elements/Lines.elm (the red square follows the mouse)

squares.elm

import Mouse

# Separating main and squares was key to making lift work
# I don't know how to convert Signal (Int,Int) to Signal (Float,Float)
# so I separated x and y into different arguments
main = lift2 squares (toFloat <~ Mouse.x)
                     (toFloat <~ Mouse.y)

squares : Float -> Float -> Element
squares x y =
        collage 500 500
         [ move (0,0) blueSquare
         , move (x - 250,250 - y) redSquare
         ]

blueSquare : Form
blueSquare = traced (dashed blue) square

redSquare : Form
redSquare = traced (solid red) square

square : Path
square = path [ (50,50), (50,-50), (-50,-50), (-50,50), (50,50) ]