The procedure sews together neighboring contour paths, and draws resulting polygon with holes in it. The paths are extracted from 'children' property of standard contourf object, because they are closed, unlike the 'contour matrix'.
If you desire 'edgecolor' other than 'none', please use standard contour procedure.

Usage:
[poly ph] = contourfill(x,y, z, lev, varargin)

poly = cell array with x,y-coordinates of the closed-contour-paths
ph = handles to plot objects created by function fill
Other arguments refer to 'fill'.
Example:
lev = [0.5 2];
z = peaks(100);
figure(234); clf; hold on;
contourfill([],[], z' , lev, facecolor', 'b', 'facealpha', 0.3 );
contourfill([],[], flipud(z), lev, 'facecolor', 'g', 'facealpha', 0.3 );
contourfill([],[], fliplr(z), lev, 'facecolor', 'r', 'facealpha', 0.3 );