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+Two for-loop variants are supported: a C-style counting for loop
+consisting of an initialization expression, a test condition
+and a step expression and a for-in-loop variant which allows
+enumerating properties of objects or items of arrays.
+
+Additionally, utpl supports an alternative syntax suitable for
+template block tags.
+
+
+-- Expect stdout --
+A simple counting for-loop:
+Iteration 0
+Iteration 1
+Iteration 2
+Iteration 3
+Iteration 4
+Iteration 5
+Iteration 6
+Iteration 7
+Iteration 8
+Iteration 9
+
+If the loop body consists of only one statement, the curly braces
+may be omitted:
+Iteration 0
+Iteration 1
+Iteration 2
+Iteration 3
+Iteration 4
+Iteration 5
+Iteration 6
+Iteration 7
+Iteration 8
+Iteration 9
+
+Any of the init-, test- and increment expressions may be omitted.
+
+Loop without initialization statement:
+Iteration null
+Iteration 1
+Iteration 2
+
+Loop without test statement:
+Iteration 0
+Iteration 1
+Iteration 2
+
+Loop without init-, test- or increment statement:
+Iteration 1
+Iteration 2
+Iteration 3
+
+For-in loop enumerating object properties:
+Key: foo
+Key: bar
+
+For-in loop enumerating array items:
+Item: one
+Item: two
+Item: three
+
+A counting for-loop using the alternative syntax:
+Iteration 0
+Iteration 1
+Iteration 2
+Iteration 3
+Iteration 4
+Iteration 5
+Iteration 6
+Iteration 7
+Iteration 8
+Iteration 9
+
+A for-in loop using the alternative syntax:
+Item 123
+Item 456
+Item 789
+
+For-in and counting for loops may declare variables:
+Iteration 0
+Iteration 1
+Iteration 2
+
+Item 123
+Item 456
+Item 789
+-- End --
+
+-- Testcase --
+A simple counting for-loop:
+{%
+	for (i = 0; i < 10; i++) {
+		print("Iteration ");
+		print(i);
+		print("\n");
+	}
+%}
+
+If the loop body consists of only one statement, the curly braces
+may be omitted:
+{%
+ 	for (i = 0; i < 10; i++)
+		print("Iteration ", i, "\n");
+%}
+
+Any of the init-, test- and increment expressions may be omitted.
+
+Loop without initialization statement:
+{%
+	for (; j < 3; j++)
+		print("Iteration " + j + "\n");
+%}
+
+Loop without test statement:
+{%
+	for (j = 0;; j++) {
+		if (j == 3)
+			break;
+
+		print("Iteration ", j, "\n");
+	}
+%}
+
+Loop without init-, test- or increment statement:
+{%
+	for (;;) {
+		if (k++ == 3)
+			break;
+
+		print("Iteration ", k, "\n");
+	}
+%}
+
+For-in loop enumerating object properties:
+{%
+	obj = { foo: true, bar: false };
+	for (key in obj)
+		print("Key: ", key, "\n");
+%}
+
+For-in loop enumerating array items:
+{%
+	arr = [ "one", "two", "three" ];
+	for (item in arr)
+		print("Item: ", item, "\n");
+%}
+
+A counting for-loop using the alternative syntax:
+{% for (x = 0; x < 10; x++): -%}
+Iteration {{ x }}
+{% endfor %}
+
+A for-in loop using the alternative syntax:
+{% for (n in [123, 456, 789]): -%}
+Item {{ n }}
+{% endfor %}
+
+For-in and counting for loops may declare variables:
+{% for (let i = 0; i < 3; i++): %}
+Iteration {{ i }}
+{% endfor %}
+
+{% for (let n in [123, 456, 789]): %}
+Item {{ n }}
+{% endfor %}
+-- End --
+
+
+By specifying two loop variables in for-in loop expressions, keys
+and values can be iterated simultaneously.
+
+-- Expect stdout --
+true
+false
+123
+456
+[ 0, true ]
+[ 1, false ]
+[ 2, 123 ]
+[ 3, 456 ]
+foo
+bar
+baz
+qrx
+[ "foo", true ]
+[ "bar", false ]
+[ "baz", 123 ]
+[ "qrx", 456 ]
+-- End --
+
+-- Testcase --
+{%
+	let arr = [ true, false, 123, 456 ];
+	let obj = { foo: true, bar: false, baz: 123, qrx: 456 };
+
+	// iterating arrays with one loop variable yields the array values
+	for (let x in arr)
+		print(x, "\n");
+
+	// iterating arrays with two loop variables yields the array indexes
+	// and their corresponding values
+	for (let x, y in arr)
+		print([x, y], "\n");
+
+	// iterating objects with one loop variable yields the object keys
+	for (let x in obj)
+		print(x, "\n");
+
+	// iterating objects with two loop variables yields the object keys
+	// and their corresponding values
+	for (let x, y in obj)
+		print([x, y], "\n");
+%}
+-- End --
+
+
+Ensure that for-in loop expressions with more than two variables are
+rejected.
+
+-- Expect stderr --
+Syntax error: Unexpected token
+Expecting ';'
+In line 2, byte 24:
+
+ `    for (let x, y, z in {})`
+  Near here ----------------^
+
+
+-- End --
+
+-- Testcase --
+{%
+	for (let x, y, z in {})
+		;
+%}
+-- End --
+
+
+Ensure that assignments in for-in loop expressions are rejected.
+
+-- Expect stderr --
+Syntax error: Unexpected token
+Expecting ';'
+In line 2, byte 25:
+
+ `    for (let x = 1, y in {})`
+  Near here -----------------^
+
+
+-- End --
+
+-- Testcase --
+{%
+	for (let x = 1, y in {})
+		;
+%}
+-- End --
+
+
+Ensure that too short for-in loop expressions are rejected (1/2).
+
+-- Expect stderr --
+Syntax error: Unexpected token
+Expecting ';'
+In line 2, byte 12:
+
+ `    for (let x)`
+  Near here ----^
+
+
+-- End --
+
+-- Testcase --
+{%
+	for (let x)
+		;
+%}
+-- End --
+
+
+Ensure that too short for-in loop expressions are rejected (2/2).
+
+-- Expect stderr --
+Syntax error: Unexpected token
+Expecting ';'
+In line 2, byte 15:
+
+ `    for (let x, y)`
+  Near here -------^
+
+
+-- End --
+
+-- Testcase --
+{%
+	for (let x, y)
+		;
+%}
+-- End --