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diff --git a/docs/history/15-o3/code/tests/umd.zc b/docs/history/15-o3/code/tests/umd.zc
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+++ b/docs/history/15-o3/code/tests/umd.zc
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+// lists as [len, items...], items owned by the list
+.u mklist(n) {
+	let l = new(n + 1);
+	l[0] = 0;
+	return u*l;
+}
+fn push(.m l, .d item) { l[l[0] + 1] = d*item; l[0] = l[0] + 1; return 0; }
+fn sum(.m l) { let s = 0, i = 1; while (i <= l[0]) { s += l[i][0]; i++; } return s; }
+.u box(v) { let b = new(1); b[0] = v; return u*b; }
+fn consume(.d b) { return b[0]; }
+
+fn main()
+{
+	let base = live_objects();
+	{
+		let l = mklist(8);		// u from mklist arrives m*here
+		let i = 0;
+		while (i < 5) {
+			let b = box(i * 10);	// m in the loop body
+			d*b;			// give it down
+			push(l, b);
+			i++;
+		}
+		putn(sum(l)); putc(' ');
+		putn(live_objects() - base); putc(' ');	// list + 5 boxes
+	}
+	putn(live_objects() - base); putc(' ');	// freed at the block's end, children too
+
+	// u handed up one block by assignment, and as a block value
+	let outer;
+	{
+		let t = box(7);
+		u*t;
+		outer = t;
+	}
+	let v = { let w = box(8); u*w };
+	putn(outer[0] + v[0]); putc(' ');
+
+	// d given away to a callee
+	let g = box(99);
+	putn(consume(d*g)); putc(' ');
+
+	// containers: child takes its parent's tag
+	let p = new(2), c = new(1);
+	c[0] = 5;
+	p[0] = c;
+	p[1] = new(3);
+	putn(p[0][0]); putc(' ');
+	putn(live_objects() - base); putc(10);
+	return 0;
+}