It is in the downloads repo as part of "Collection of test games" It's literally just this though:
//THE MODE7 EFFECT
//Set it as a renderscript to see it in action!
//(note: sprites are stretched by the effect too!)
var MapImage;
var x1;
var x2;
var y1;
var y2;
//Modify x1 and x2 to change the top blit map x position. Not recommended.
//Modify x3 and x4 to stretch the map more. Make 30 bigger to strech more, and smaller to stretch less.
//If x1 and x2 == x3 and x4 then the map will blit like it would normally show.
x1 = 0;
x2 = GetScreenWidth();
x3 = GetScreenWidth()+50;
x4 = -50;
//Modify both y1 and y2 to change the height from the top of the mode7 map.
//Modify y3 and y4 to change the height from the bottom.
y1 = 0;
y2 = 0;
y3 = GetScreenHeight();
y4 = GetScreenHeight();
var black = CreateColor(0,0,0);
function WorldmapEffect()
{
MapImage = GrabImage(0, 0, GetScreenWidth(), GetScreenHeight());
//Before we start, cover the original map with black
//Turned off by default, but turn it on if you'll need to stetch maps so the old unedited map doesn't
//Show under it. Note that the effect then will be slightly slower and won't work on the DirectX driver.
//Rectangle(0,0,GetScreenWidth(),GetScreenHeight(), black);
MapImage.transformBlit(x1, y1, x2, y2, x3, y3, x4, y4);
//Draw the REAL sprite on the screen.
//var frame =
//RealSprite.images[].blit(160, 120);
}