diff --git a/optvm/src/main/java/com/compilerprogramming/ezlang/compiler/ExitSSA.java b/optvm/src/main/java/com/compilerprogramming/ezlang/compiler/ExitSSA.java
index 5bac8f8..7cec37a 100644
--- a/optvm/src/main/java/com/compilerprogramming/ezlang/compiler/ExitSSA.java
+++ b/optvm/src/main/java/com/compilerprogramming/ezlang/compiler/ExitSSA.java
@@ -7,6 +7,9 @@
  * Implementation is based on description in
  * 'Practical Improvements to the Construction and Destruction
  * of Static Single Assignment Form' by Preston Briggs.
+ *
+ * The JikesRVM LeaveSSA implements a version of the
+ * same algorithm.
  */
 public class ExitSSA {
 
@@ -70,8 +73,11 @@ private void replaceUses(Instruction i) {
     }
 
     static class CopyItem {
+        /** Phi input can be a register or a constant so we record the operand */
         final Operand src;
+        /** The phi destination */
         final Register dest;
+        /** The basic block where the phi was present */
         final BasicBlock destBlock;
         boolean removed;
 
@@ -130,11 +136,19 @@ private void scheduleCopies(BasicBlock block, List<Integer> pushed) {
                    a copy target that is live, we must preserve the live
                    value in a temporary name and rewrite subsequent uses to
                    refer to the temporary name.
+
+                   This captures the cases when the result of a phi
+                   in a control successor is live on exit of the current block.
+                   This means that it is incorrect to simply insert a copy
+                   of the destination in the current block. So we rename
+                   the destination to a new temporary, and record the renaming
+                   so that the dominator blocks get the new name. Comment adapted
+                   from JikesRVM LeaveSSA
                  */
                 if (block.liveOut.get(dest.id)) {
                     /* Insert a copy from dest to a new temp t at phi node defining dest */
                     final Register t = addMoveToTempAfterPhi(destBlock, dest);
-                    stacks[dest.id].push(t);
+                    stacks[dest.id].push(t);    // record the temp name
                     pushed.add(dest.id);
                 }
                 /* Insert a copy operation from map[src] to dest at end of BB */
@@ -158,6 +172,13 @@ else if (src instanceof Operand.ConstantOperand srcConstantOperand) {
                cycle of references, it must insert a copy to a temporary
                that breaks the cycle. Then we can schedule the copies to
                respect the dependencies implied by the phi functions.
+
+               An empty work list with work remaining in the copy set
+               implies a cycle in the dependencies amongst copies. To break
+               the cycle copy the destination of an arbitrary member of the
+               copy set to a temporary. This destination has therefore been
+               saved and can be safely overwritten. So then add the copy to the
+               work list. Comment adapted from JikesRVM LeaveSSA.
              */
             if (!copySet.isEmpty()) {
                 CopyItem copyItem = copySet.remove(0);
@@ -220,6 +241,7 @@ private void addMoveAtBBEnd(BasicBlock block, Register src, Register dest) {
         var inst = new Instruction.Move(new Operand.RegisterOperand(src), new Operand.RegisterOperand(dest));
         insertAtEnd(block, inst);
     }
+    /* Insert a copy from constant src to dst at end of BB */
     private void addMoveAtBBEnd(BasicBlock block, Operand.ConstantOperand src, Register dest) {
         var inst = new Instruction.Move(src, new Operand.RegisterOperand(dest));
         insertAtEnd(block, inst);
diff --git a/optvm/src/test/java/com/compilerprogramming/ezlang/compiler/TestSSATransform.java b/optvm/src/test/java/com/compilerprogramming/ezlang/compiler/TestSSATransform.java
index d2b4f04..17ff310 100644
--- a/optvm/src/test/java/com/compilerprogramming/ezlang/compiler/TestSSATransform.java
+++ b/optvm/src/test/java/com/compilerprogramming/ezlang/compiler/TestSSATransform.java
@@ -1045,5 +1045,280 @@ func foo() {
 
     }
 
+    @Test
+    public void testParallelAssign() {
+        String src = """
+                func foo(n: Int)->Int {
+                   var a = 1
+                   var b = 2
+                   
+                   while (n > 0) {
+                        var t = a
+                        a = b
+                        b = t
+                        n = n - 1
+                   }
+                   return a
+                }
+                """;
+        String result = compileSrc(src);
+        System.out.println(result);
+    }
+
+    @Test
+    public void testSSA1() {
+        String src = """
+                func foo()->Int {
+                    var a = 5
+                    var b = 10
+                    var c = a + b
+                    return c
+                }
+                """;
+        String result = compileSrc(src);
+        System.out.println(result);
+    }
+
+    @Test
+    public void testSSA2() {
+        String src = """
+                func foo()->Int {
+                    var a = 5
+                    a = a + 1;
+                    return a
+                }
+                """;
+        String result = compileSrc(src);
+        System.out.println(result);
+    }
+
+    @Test
+    public void testSSA3() {
+        String src = """
+                func foo()->Int {
+                    var a = 5
+                    if (a > 3) {
+                        a = 10
+                    } else {
+                        a = 20
+                    }
+                    return a
+                }
+                """;
+        String result = compileSrc(src);
+        System.out.println(result);
+    }
+
+    @Test
+    public void testSSA4() {
+        String src = """
+                func foo()->Int {
+                    var a = 0
+                    while (a < 5) {
+                        a = a + 1;
+                    }
+                    return a
+                }
+                """;
+        String result = compileSrc(src);
+        System.out.println(result);
+    }
+
+    @Test
+    public void testSSA5() {
+        String src = """
+                func foo()->Int {
+                    var a = 0
+                    var b = 10
+                    if (b > 5) {
+                        if (a < 5) {
+                            a = 5
+                        } else {
+                            a = 15
+                        }
+                    } else {
+                        a = 20
+                    }
+                    return a
+                }
+                """;
+        String result = compileSrc(src);
+        System.out.println(result);
+    }
+
+    @Test
+    public void testSSA6() {
+        String src = """
+                func foo()->Int {
+                    var arr = new [Int] {1, 2};
+                    arr[0] = 10
+                    var x = arr[0]
+                    return x
+                }
+                """;
+        String result = compileSrc(src);
+        System.out.println(result);
+    }
+
+    @Test
+    public void testSSA7() {
+        String src = """
+        func add(x: Int, y : Int)->Int {
+            return x + y
+        }
+        func main()->Int {
+            var a = 5
+            var b = 10
+            var c = add(a, b)
+            return c
+        }
+""";
+        String result = compileSrc(src);
+        System.out.println(result);
+    }
+
+    @Test
+    public void testSSA8() {
+        String src = """
+        func main()->Int {
+            var a = 0
+            var b = 1
+            while (a < 10) {
+                a = a + 2
+            }
+            while (b < 20) {
+                b = b + 3
+            }
+            return a + b
+        }
+""";
+        String result = compileSrc(src);
+        System.out.println(result);
+    }
+
+    @Test
+    public void testSSA9() {
+        String src = """
+        func main()->Int {
+            var a = 0
+            var b = 0
+            var i = 0
+            var j = 0
+            while (i < 3) {
+                j = 0
+                while (j < 2) {
+                    a = a + 1
+                    i = j + 1
+                }
+                b = b + 1;
+                i = i + 1    
+            }
+            return a + b
+        }
+""";
+        String result = compileSrc(src);
+        System.out.println(result);
+    }
+
+    @Test
+    public void testSSA10() {
+        String src = """
+        func main()->Int {
+            var sum = 0
+            var i = 0
+            var j = 0
+            while (i < 5) {
+                j = 0
+                while (j < 5) {
+                    if (j % 2 == 0) 
+                        sum = sum + j
+                    j = j + 1    
+                }
+                i = i + 1    
+            }
+            return sum
+        }
+""";
+        String result = compileSrc(src);
+        System.out.println(result);
+    }
+
+    @Test
+    public void testSSA11() {
+        String src = """
+        func main()->Int {
+            var a = 0
+            var i = 0
+            var j = 0
+            while (i < 3) {
+                j = 0
+                while (j < 3) {
+                    if (i == j) 
+                        a = a + i + j
+                    else if (i > j)
+                        a = a - 1
+                    j = j + 1        
+                }
+                i = i + 1    
+            }
+            return a
+        }
+""";
+        String result = compileSrc(src);
+        System.out.println(result);
+    }
+
+    @Test
+    public void testSSA12() {
+        String src = """
+        func main()->Int {
+            var count = 0
+            var i = 0
+            var j = 0
+            while (i < 5) {
+                j = 0
+                while (j < 5) {
+                    if (i + j > 5)
+                        break
+                    if (i == j) {
+                        j = j + 1
+                        continue
+                    }
+                    count = count + 1
+                    j = j + 1
+                }
+                i = i + 1
+            }
+            return count
+        }
+""";
+        String result = compileSrc(src);
+        System.out.println(result);
+    }
+
+    @Test
+    public void testSSA13() {
+        String src = """
+        func main()->Int {
+            var outerSum = 0
+            var innerSum = 0
+            var i = 0
+            var j = 0
+            while (i < 4) {
+                j = 0
+                while (j < 4) {
+                    if ((i + j) % 2 == 0)
+                        innerSum = innerSum + j
+                    j = j + 1
+                }
+                outerSum = outerSum + innerSum
+                i = i + 1
+            }
+            return outerSum
+        }
+""";
+        String result = compileSrc(src);
+        System.out.println(result);
+    }
 
 }
\ No newline at end of file
diff --git a/parser/src/main/java/com/compilerprogramming/ezlang/parser/Parser.java b/parser/src/main/java/com/compilerprogramming/ezlang/parser/Parser.java
index de65e19..2249d4d 100644
--- a/parser/src/main/java/com/compilerprogramming/ezlang/parser/Parser.java
+++ b/parser/src/main/java/com/compilerprogramming/ezlang/parser/Parser.java
@@ -348,7 +348,6 @@ private AST.Expr parsePrimary(Lexer lexer) {
             case PUNCT -> {
                 /* Nested expression */
                 matchPunctuation(lexer, "(");
-                nextToken(lexer);
                 var x = parseBool(lexer);
                 matchPunctuation(lexer, ")");
                 return x;