Matlab: how to draw a 2D geometry with curved lines in pdetool box

I'm using the pde toolbox in Matlab to solve the diffusion equation in 2D spatial domain. My geometry is irregular, i.e., the edges are curved lines. How can I draw that in the pdetool box ? Say one edge is represented by this equation 3x^2-x^3-x+2 for x from 0 to 3