diff --git a/examples/perlin_noise_cylinder.scad b/examples/perlin_noise_cylinder.scad
index bfd51612..53fdf059 100644
--- a/examples/perlin_noise_cylinder.scad
+++ b/examples/perlin_noise_cylinder.scad
@@ -24,18 +24,18 @@ module perlin_noise_cylinder(radius, height, thickness_scale, step) {
     ];
 
     seed = rand(0, 256);
+    leng_row = len(surface_inside[0]);
     surface_outside = [
             for(ri = [0:len(surface_inside) - 1])
                 let(
                     row = surface_inside[ri],
-                    leng_row = len(row),
                     row_for_noise = concat(slice(row, 0, leng_row - 1), [[0, row[leng_row - 1][1], 0]]),
                     ns = pnoise2s(row_for_noise, seed)
                 )
-                    [
-                        for(ci = [0:len(ns) - 1])
-                            [surface_inside[ri][ci][0], surface_inside[ri][ci][1], thickness_scale * (ns[ci] + 1)]
-                    ]
+                [
+                    for(ci = [0:len(ns) - 1])
+                        [surface_inside[ri][ci][0], surface_inside[ri][ci][1], thickness_scale * (ns[ci] + 1)]
+                ]
         ];
 
     size_div_10 = size / 10;
@@ -46,14 +46,14 @@ module perlin_noise_cylinder(radius, height, thickness_scale, step) {
                     ptf_bend(size_div_10, p, radius_div_10, 360)
                 ]
         ];
-    t_surface_insde = [
+    t_surface_inside = [
         for(row = surface_inside)
             [for(p = row)
                 ptf_bend(size_div_10, p, radius_div_10, 360)
             ]
     ];
  
-    sf_solidify(t_surface_outside, t_surface_insde);
+    sf_solidify(t_surface_outside, t_surface_inside);
 }
 
 perlin_noise_cylinder(radius, height, thickness_scale, step);
\ No newline at end of file