diff --git a/_docs/mod/core.md b/_docs/mod/core.md
index 6b9e3a7..37bdbbe 100644
--- a/_docs/mod/core.md
+++ b/_docs/mod/core.md
@@ -50,10 +50,10 @@ If COL is a list, `first` will consume from index 0 and will continue until eith
 satisfies the predicate, or until the end of the list is reached. If COL is an iterator, `first` will continue 
 consuming values until a value satisfying the predicate is found, or until the iterator is exhausted.
 
-### foreach
+### for
 
 ```
-foreach COL BLOCK
+for COL BLOCK
 ```
 
 Iterates BLOCK over every element of the sequence.
@@ -63,16 +63,16 @@ If COL is a hash, BLOCK receives both the key and value of each element.
 
 BLOCK can call `break` and `continue` which will exit out of the loop, or jump to the start of the next iteration
 respectively.
-The return value of `foreach` will be the result of the last iteration, unless `break` is called with a value.
+The return value of `for` will be the result of the last iteration, unless `break` is called with a value.
 
 This is implemented as a macro but can be used in a pipeline. 
 
 ```
-foreach [1 2 3] { |e|
+for [1 2 3] { |e|
   echo "Element = $e"
 }
 
-[a:"one" b:"two"] | foreach { |k v|
+[a:"one" b:"two"] | for { |k v|
   echo "Key $k = $v"
 }
 ```
@@ -167,7 +167,7 @@ If FROM and TO are equal, or if FROM is unspecified and TO is 0, then the sequen
 If -inc is specified, then the sequence will step towards TO inclusively.
 
 ```
-foreach (seq 5) { |i|
+for (seq 5) { |i|
   echo $i
 }
 ```
@@ -182,3 +182,11 @@ Sets the value of variable NAME to VALUE. Any variable with NAME will be checked
 within the scope first, including any parent scopes, before a new variable is defined.
 Any new variables will only be defined with the current scope.
 
+### set!
+
+```
+set! NAME VALUE
+```
+
+Sets the value of variable NAME to VALUE. VALUE must be non-null otherwise `set!` will raise an error.
+
diff --git a/ucl/inst.go b/ucl/inst.go
index a3ea956..d07bcc6 100644
--- a/ucl/inst.go
+++ b/ucl/inst.go
@@ -104,7 +104,7 @@ func New(opts ...InstOption) *Inst {
 	rootEC.addCmd("error", invokableFunc(errorBuiltin))
 
 	rootEC.addMacro("if", macroFunc(ifBuiltin))
-	rootEC.addMacro("foreach", macroFunc(foreachBuiltin))
+	rootEC.addMacro("for", macroFunc(foreachBuiltin))
 	rootEC.addMacro("proc", macroFunc(procBuiltin))
 	rootEC.addMacro("try", macroFunc(tryBuiltin))
 
diff --git a/ucl/inst_test.go b/ucl/inst_test.go
index 1faa97c..931c924 100644
--- a/ucl/inst_test.go
+++ b/ucl/inst_test.go
@@ -179,7 +179,7 @@ func TestInst_MissingVarHandler(t *testing.T) {
 
 var parseComments1 = `
 	proc lookup { |file|
-		foreach { |toks|
+		for { |toks|
 		}
 		# this use to fail
 	}
@@ -187,7 +187,7 @@ var parseComments1 = `
 
 var parseComments2 = `
 	proc lookup { |file|
-		foreach { |toks|
+		for { |toks|
 		}
 
 		# this use to fail
@@ -199,7 +199,7 @@ var parseComments2 = `
 
 var parseComments3 = `
 	proc lookup { |file|
-		foreach { |toks|
+		for { |toks|
 		}
 
 		# this use to fail
@@ -211,7 +211,7 @@ var parseComments3 = `
 
 var parseComments4 = `
 	proc lookup { |file|
-		foreach { |toks|
+		for { |toks|
 		}	
 	}
 # this use to fail`
diff --git a/ucl/testbuiltins_test.go b/ucl/testbuiltins_test.go
index f843150..7aa5644 100644
--- a/ucl/testbuiltins_test.go
+++ b/ucl/testbuiltins_test.go
@@ -129,7 +129,7 @@ func TestBuiltins_Echo(t *testing.T) {
 		{desc: "interpolated string 3", expr: `echo "separate\nlines\n\tand tabs"`, want: "separate\nlines\n\tand tabs\n"},
 		{desc: "interpolated string 4", expr: `set what "Hello" ; set where "world" ; echo "$what, $where"`, want: "Hello, world\n"},
 		{desc: "interpolated string 5", expr: `
-			foreach [123 "foo" true ()] { |x|
+			for [123 "foo" true ()] { |x|
                 echo "[[$x]]"
 			}
 		`, want: "[[123]]\n[[foo]]\n[[true]]\n[[]]\n"},
@@ -210,8 +210,8 @@ func TestBuiltins_If(t *testing.T) {
 		{desc: "compressed else", expr: `if $x { echo "true" } else { echo "false" }`, want: "false\n(nil)\n"},
 		{desc: "compressed if", expr: `if $x { echo "x" } elif $y { echo "y" } else { echo "false" }`, want: "false\n(nil)\n"},
 		{desc: "if of itr 1", expr: `set i (itr) ; if $i { echo "more" } else { echo "none" }`, want: "more\n(nil)\n"},
-		{desc: "if of itr 2", expr: `set i (itr) ; foreach (seq 1) { head $i } ; if $i { echo "more" } else { echo "none" }`, want: "more\n(nil)\n"},
-		{desc: "if of itr 3", expr: `set i (itr) ; foreach (seq 3) { head $i } ; if $i { echo "more" } else { echo "none" }`, want: "none\n(nil)\n"},
+		{desc: "if of itr 2", expr: `set i (itr) ; for (seq 1) { head $i } ; if $i { echo "more" } else { echo "none" }`, want: "more\n(nil)\n"},
+		{desc: "if of itr 3", expr: `set i (itr) ; for (seq 3) { head $i } ; if $i { echo "more" } else { echo "none" }`, want: "none\n(nil)\n"},
 		{desc: "if of itr 4", expr: `set i (itr | map { |x| add 2 $x }) ; if $i { echo "more" } else { echo "none" }`, want: "more\n(nil)\n"},
 		{desc: "if of itr 5", expr: `set i (itr | filter { |x| () }) ; if $i { echo "more" } else { echo "none" }`, want: "none\n(nil)\n"},
 		{desc: "if of itr 6", expr: `set i (itr | filter { |x| 1 }) ; if $i { echo "more" } else { echo "none" }`, want: "more\n(nil)\n"},
@@ -430,26 +430,26 @@ func TestBuiltins_Try(t *testing.T) {
 	}
 }
 
-func TestBuiltins_ForEach(t *testing.T) {
+func TestBuiltins_For(t *testing.T) {
 	tests := []struct {
 		desc string
 		expr string
 		want string
 	}{
 		{desc: "iterate over list 1", expr: `
-			foreach ["1" "2" "3"] { |v|
+			for ["1" "2" "3"] { |v|
 				echo $v
 			}`, want: "1\n2\n3\n(nil)\n"},
 		{desc: "iterate over list 2",
-			expr: `foreach ["1" "2" "3"] echo`,
+			expr: `for ["1" "2" "3"] echo`,
 			want: "1\n2\n3\n(nil)\n"},
 		// TODO: hash is not sorted, so need to find a way to sort it
 		{desc: "iterate over map 1", expr: `
-			foreach [a:"1"] { |k v| echo $k "=" $v }`, want: "a=1\n(nil)\n"},
+			for [a:"1"] { |k v| echo $k "=" $v }`, want: "a=1\n(nil)\n"},
 		{desc: "iterate over map 2", expr: `
-			foreach [a:"1"] echo`, want: "a1\n(nil)\n"},
-		{desc: "iterate via pipe", expr: `["2" "4" "6"] | foreach { |x| echo $x }`, want: "2\n4\n6\n(nil)\n"},
-		{desc: "iterate from iterator 1", expr: `itr | foreach { |x| echo $x }`, want: "1\n2\n3\n(nil)\n"},
+			for [a:"1"] echo`, want: "a1\n(nil)\n"},
+		{desc: "iterate via pipe", expr: `["2" "4" "6"] | for { |x| echo $x }`, want: "2\n4\n6\n(nil)\n"},
+		{desc: "iterate from iterator 1", expr: `itr | for { |x| echo $x }`, want: "1\n2\n3\n(nil)\n"},
 	}
 
 	for _, tt := range tests {
@@ -473,29 +473,29 @@ func TestBuiltins_Break(t *testing.T) {
 		want string
 	}{
 		{desc: "break unconditionally returning nothing", expr: `
-			foreach ["1" "2" "3"] { |v|
+			for ["1" "2" "3"] { |v|
 				break
 				echo $v
 			}`, want: "(nil)\n"},
 		{desc: "break conditionally returning nothing", expr: `
-			foreach ["1" "2" "3"] { |v|
+			for ["1" "2" "3"] { |v|
 				echo $v
 				if (eq $v "2") { break }
 			}`, want: "1\n2\n(nil)\n"},
 		{desc: "break inner loop only returning nothing", expr: `
-			foreach ["a" "b"] { |u|
-				foreach ["1" "2" "3"] { |v|
+			for ["a" "b"] { |u|
+				for ["1" "2" "3"] { |v|
 					echo $u $v
 					if (eq $v "2") { break }
 				}
 			}`, want: "a1\na2\nb1\nb2\n(nil)\n"},
 		{desc: "break returning value 1", expr: `
-			echo (foreach ["1" "2" "3"] { |v|
+			echo (for ["1" "2" "3"] { |v|
 				echo $v
 				if (eq $v "2") { break "hello" }
 			})`, want: "1\n2\nhello\n(nil)\n"},
 		{desc: "break returning value 2", expr: `
-			echo (foreach (itr) { |v|
+			echo (for (itr) { |v|
 				echo $v
 				if (eq $v 2) { break "hello" }
 			})`, want: "1\n2\nhello\n(nil)\n"},
@@ -522,20 +522,20 @@ func TestBuiltins_Continue(t *testing.T) {
 		want string
 	}{
 		{desc: "continue unconditionally", expr: `
-			foreach ["1" "2" "3"] { |v|
+			for ["1" "2" "3"] { |v|
 				echo $v "s"
 				continue
 				echo $v "e"
 			}`, want: "1s\n2s\n3s\n(nil)\n"},
 		{desc: "conditionally conditionally", expr: `
-			foreach ["1" "2" "3"] { |v|
+			for ["1" "2" "3"] { |v|
 				echo $v "s"
 				if (eq $v "2") { continue }
 				echo $v "e"
 			}`, want: "1s\n1e\n2s\n3s\n3e\n(nil)\n"},
 		{desc: "continue inner loop only", expr: `
-			foreach ["a" "b"] { |u|
-				foreach ["1" "2" "3"] { |v|	
+			for ["a" "b"] { |u|
+				for ["1" "2" "3"] { |v|	
 					if (eq $v "2") { continue }
 					echo $u $v
 				}
@@ -726,7 +726,7 @@ func TestBuiltins_Return(t *testing.T) {
 			`, want: "Greet the\nHello, moon\n(nil)\n"},
 		{desc: "return in loop", expr: `
 			proc countdown { |nums|
-				foreach $nums { |n|
+				for $nums { |n|
 					echo $n
 					if (eq $n 3) {
 						return "abort"
@@ -751,7 +751,7 @@ func TestBuiltins_Return(t *testing.T) {
 			}
 
 			proc test-thing {
-				foreach [1 2 3] { |x|
+				for [1 2 3] { |x|
 					do-thing {
 						echo $x
 					}
@@ -766,7 +766,7 @@ func TestBuiltins_Return(t *testing.T) {
 			}
 
 			proc test-thing {
-				foreach [1 2 3] { |x|
+				for [1 2 3] { |x|
 					do-thing (proc {
 						echo $x
 					})
@@ -781,7 +781,7 @@ func TestBuiltins_Return(t *testing.T) {
 			}
 
 			proc test-thing {
-				foreach [1 2 3] { |x|
+				for [1 2 3] { |x|
 					set myClosure (proc { echo $x })
 					do-thing $myClosure
 				}
@@ -800,7 +800,7 @@ func TestBuiltins_Return(t *testing.T) {
 				}
 			}
 
-			foreach (test-thing) { |y| call $y }
+			for (test-thing) { |y| call $y }
 		`, want: "1\n2\n3\n(nil)\n"},
 		{desc: "check closure 5", expr: `
 			proc do-thing { |p|
@@ -815,7 +815,7 @@ func TestBuiltins_Return(t *testing.T) {
 			}
 
 			set hello "xx"
-			foreach (test-thing) { |y| call $y ; echo $hello }
+			for (test-thing) { |y| call $y ; echo $hello }
 		`, want: "1\nxx\n2\nxx\n3\nxx\n(nil)\n"},
 		{desc: "check closure 7", expr: `
 			proc do-thing { |p|
@@ -832,7 +832,7 @@ func TestBuiltins_Return(t *testing.T) {
 			}
 
 			set hello "xx"
-			foreach (test-thing) { |y| call $y ; echo $hello }
+			for (test-thing) { |y| call $y ; echo $hello }
 		`, want: "3\nxx\n3\nxx\n3\nxx\n(nil)\n"},
 		{desc: "check closure 7", expr: `
 			proc do-thing { |p|
@@ -850,7 +850,7 @@ func TestBuiltins_Return(t *testing.T) {
 			}
 
 			set hello "xx"
-			foreach (test-thing) { |y| call $y ; echo $hello }
+			for (test-thing) { |y| call $y ; echo $hello }
 		`, want: "1\nxx\n2\nxx\n3\nxx\n(nil)\n"},
 	}
 
@@ -965,7 +965,7 @@ func TestBuiltins_Map(t *testing.T) {
 			set add2 (proc { |x| add $x 2 })
 		
 			set l (itr | map $add2)
-			foreach $l { |x| echo $x }
+			for $l { |x| echo $x }
 			`, want: "3\n4\n5\n(nil)\n"},
 	}
 
@@ -1218,7 +1218,7 @@ func TestBuiltins_Filter(t *testing.T) {
 		}},
 		{desc: "filter map 3", expr: `filter [alpha:"hello" bravo:"world"] { |k v| eq $v "alpha" }`, want: map[string]any{}},
 
-		{desc: "filter itr 1", expr: `set s "" ; itr | filter { |x| ne $x 2 } | foreach { |x| set s "$s $x" }; $s`, want: " 1 3"},
+		{desc: "filter itr 1", expr: `set s "" ; itr | filter { |x| ne $x 2 } | for { |x| set s "$s $x" }; $s`, want: " 1 3"},
 	}
 
 	for _, tt := range tests {
diff --git a/ucl/userbuiltin_test.go b/ucl/userbuiltin_test.go
index 149e988..816cd48 100644
--- a/ucl/userbuiltin_test.go
+++ b/ucl/userbuiltin_test.go
@@ -187,7 +187,7 @@ func TestInst_SetBuiltin(t *testing.T) {
 			wantOut string
 		}{
 			{descr: "return as is", expr: `countTo3`, want: []string{"1", "2", "3"}},
-			{descr: "iterate over", expr: `foreach (countTo3) { |x| echo $x }`, wantOut: "1\n2\n3\n"},
+			{descr: "iterate over", expr: `for (countTo3) { |x| echo $x }`, wantOut: "1\n2\n3\n"},
 		}
 
 		for _, tt := range tests {
@@ -222,7 +222,7 @@ func TestInst_SetBuiltin(t *testing.T) {
 		}{
 			{descr: "return as is", expr: `getOpaque`, wantErr: false},
 			{descr: "carry around ok", expr: `set x (getOpaque) ; $x`, wantErr: false},
-			{descr: "iterate over", expr: `foreach (countTo3) { |x| echo $x }`, wantErr: true},
+			{descr: "iterate over", expr: `for (countTo3) { |x| echo $x }`, wantErr: true},
 		}
 
 		for _, tt := range tests {