diff --git a/tcl/difference-of-squares/difference-of-squares.tcl b/tcl/difference-of-squares/difference-of-squares.tcl
index 5d26ffd1..71198eb5 100644
--- a/tcl/difference-of-squares/difference-of-squares.tcl
+++ b/tcl/difference-of-squares/difference-of-squares.tcl
@@ -1,9 +1,9 @@
 proc squareOfSum {number} {
-    return [expr ($number * ($number + 1) / 2) ** 2]
+    return [expr {($number * ($number + 1) / 2) ** 2}]
 }
 
 proc sumOfSquares {number} {
-    return [expr ($number * ($number + 1) * (2 * $number + 1) / 6)]
+    return [expr {$number * ($number + 1) * (2 * $number + 1) / 6}]
 }
 
 proc differenceOfSquares {number} {
diff --git a/tcl/difference-of-squares/run-tests-tcl.txt b/tcl/difference-of-squares/run-tests-tcl.txt
index 8e757f19..f44c59bf 100644
--- a/tcl/difference-of-squares/run-tests-tcl.txt
+++ b/tcl/difference-of-squares/run-tests-tcl.txt
@@ -21,30 +21,25 @@ warn: parsing /home/vpayno/git_vpayno/exercism-workspace/tcl/difference-of-squar
 /home/vpayno/git_vpayno/exercism-workspace/tcl/difference-of-squares/testHelpers.tcl: errors file: 1
 warn: parsing /home/vpayno/git_vpayno/exercism-workspace/tcl/difference-of-squares/difference-of-squares.tcl
 /home/vpayno/git_vpayno/exercism-workspace/tcl/difference-of-squares/difference-of-squares.tcl: parsing file /home/vpayno/git_vpayno/exercism-workspace/tcl/difference-of-squares/difference-of-squares.tcl
-/home/vpayno/git_vpayno/exercism-workspace/tcl/difference-of-squares/difference-of-squares.tcl:2: possible unintended double substitution for expr use {} <<($number>>
-/home/vpayno/git_vpayno/exercism-workspace/tcl/difference-of-squares/difference-of-squares.tcl:6: possible unintended double substitution for expr use {} <<($number>>
-/home/vpayno/git_vpayno/exercism-workspace/tcl/difference-of-squares/difference-of-squares.tcl:13: expect variable 'square' as 'numeric' but is 'string {}' <<$square>>
-/home/vpayno/git_vpayno/exercism-workspace/tcl/difference-of-squares/difference-of-squares.tcl:13: expect variable 'sum' as 'numeric' but is 'string {}' <<$sum>>
-/home/vpayno/git_vpayno/exercism-workspace/tcl/difference-of-squares/difference-of-squares.tcl: errors file: 4
-errors all: 5 (13.89% lines)
-lines: 36 in: 00:00:00 59 lines/sec: 610.17
+/home/vpayno/git_vpayno/exercism-workspace/tcl/difference-of-squares/difference-of-squares.tcl:2: error in expression missing operator <<**>>
+/home/vpayno/git_vpayno/exercism-workspace/tcl/difference-of-squares/difference-of-squares.tcl: errors file: 1
+errors all: 2 (5.56% lines)
+lines: 36 in: 00:00:00 60 lines/sec: 600.00
 commands: 5 variables: 1
-signature params 9 unknown: 5 55.56% unknown variables 0.00%
+signature params 9 unknown: 3 33.33% unknown variables 0.00%
 
-real	0m0.127s
-user	0m0.103s
-sys	0m0.025s
+real	0m0.112s
+user	0m0.100s
+sys	0m0.013s
 
 ===============================================================================
 
 Running: nagelfar -s _ ./difference-of-squares.tcl
 Checking file ./difference-of-squares.tcl
-Line   2: W Expr without braces
-Line   6: W Expr without braces
 
-real	0m0.034s
-user	0m0.026s
-sys	0m0.007s
+real	0m0.032s
+user	0m0.027s
+sys	0m0.004s
 
 ===============================================================================
 
@@ -52,17 +47,17 @@ Running: RUN_ALL=1 tclsh ./difference-of-squares.test
 difference-of-squares.test:	Total	9	Passed	9	Skipped	0	Failed	0
 
 real	0m0.010s
-user	0m0.008s
-sys	0m0.002s
+user	0m0.006s
+sys	0m0.004s
 
 
 ===============================================================================
 
 Running: misspell .
 
-real	0m0.019s
-user	0m0.023s
-sys	0m0.008s
+real	0m0.020s
+user	0m0.017s
+sys	0m0.012s
 
 ===============================================================================