Code for Q1 element for elliptic equation

Hi all , please I’m looking for a code for the rectangle Q1 finite element method ( rectangle mesh) for the following poisson equation
e*dx^2 u + dy^2 u = f with Dirichlet boundary condition on a square (0,1)x(0,1)
Where e is a positive constant.
Please help me , I didn’t found any thing about that in the sources of FreeFem++
Could you help me , thank you very much

FreeFEM uses only triangular elements.