diff --git a/vlib/compiler/comptime.v b/vlib/compiler/comptime.v
index 49e6981a8e..443a360b39 100644
--- a/vlib/compiler/comptime.v
+++ b/vlib/compiler/comptime.v
@@ -202,7 +202,7 @@ fn (p mut Parser) chash() {
 	else if hash.contains('embed') {
 		pos := hash.index('embed') + 5
 		file := hash.right(pos)
-		if p.pref.build_mode != BuildMode.default_mode {
+		if p.pref.build_mode != .default_mode {
 			p.genln('#include $file')
 		}
 	}
@@ -210,10 +210,6 @@ fn (p mut Parser) chash() {
 		// Move defines on top
 		p.cgen.includes << '#$hash'
 	}
-	else if hash == 'v' {
-		println('v script')
-		//p.v_script = true
-	}
 	// Don't parse a non-JS V file (`#-js` flag)
 	else if hash == '-js'  {
 		$if js {
diff --git a/vlib/compiler/fn.v b/vlib/compiler/fn.v
index 617ab6b317..c552079351 100644
--- a/vlib/compiler/fn.v
+++ b/vlib/compiler/fn.v
@@ -662,7 +662,12 @@ fn (p mut Parser) fn_call(f Fn, method_ph int, receiver_var, receiver_type strin
 		//println('r=$receiver.typ RT=$receiver_type')
 		if receiver.is_mut && !p.expr_var.is_mut {
 			//println('$method_call  recv=$receiver.name recv_mut=$receiver.is_mut')
-			p.error('`$p.expr_var.name` is immutable, declare it with `mut`')
+			if p.expr_var.is_for_var {
+				p.error('`$p.expr_var.name` is immutable, `for` variables' +
+					' always are')
+			}	 else {
+				p.error('`$p.expr_var.name` is immutable, declare it with `mut`')
+			}
 		}
 		if !p.expr_var.is_changed {
 			p.mark_var_changed(p.expr_var)
diff --git a/vlib/compiler/main.v b/vlib/compiler/main.v
index da6444b773..7ddfb22d2d 100644
--- a/vlib/compiler/main.v
+++ b/vlib/compiler/main.v
@@ -556,6 +556,15 @@ pub fn (v mut V) add_v_files_to_compile() {
 	for file in v.get_user_files() {
 		mut p := v.new_parser_from_file(file)
 		p.parse(.imports)
+		if p.v_script {
+			v.log('imports0:')
+			println(v.table.imports)
+			println(v.files)
+			p.import_table.register_alias('os', 'os', 0)
+			p.table.imports << 'os'
+			p.table.register_module('os')
+			println('got v script')
+		}	
 		//if p.pref.autofree {		p.scanner.text.free()		free(p.scanner)	}
 		v.add_parser(p)
 	}
@@ -609,12 +618,13 @@ pub fn (v &V) get_builtin_files() []string {
 pub fn (v &V)  get_user_files() []string {
 	mut dir := v.dir
 	v.log('get_v_files($dir)')
-	// Need to store user files separately, because they have to be added after libs, but we dont know
-	// which libs need to be added yet
+	// Need to store user files separately, because they have to be added after
+	// libs, but we dont know	which libs need to be added yet
 	mut user_files := []string
 
 	if v.pref.is_test && v.pref.is_stats {
-		user_files << [v.vroot, 'vlib', 'benchmark', 'tests', 'always_imported.v'].join( os.path_separator )
+		user_files << os.join(v.vroot, 'vlib', 'benchmark', 'tests',
+			'always_imported.v')
 	}
 	
 	// v volt/slack_test.v: compile all .v files to get the environment
@@ -624,9 +634,9 @@ pub fn (v &V)  get_user_files() []string {
 	if is_test_with_imports {
 		user_files << dir
 		pos := dir.last_index(os.path_separator)
-		dir = dir.left(pos) + os.path_separator// TODO WHY IS THIS .neEDED?
+		dir = dir.left(pos) + os.path_separator// TODO why is this needed
 	}
-	if dir.ends_with('.v') {
+	if dir.ends_with('.v') || dir.ends_with('.vsh') {
 		// Just compile one file and get parent dir
 		user_files << dir
 		dir = dir.all_before(os.path_separator)
@@ -792,7 +802,7 @@ pub fn new_v(args[]string) &V {
 		*/
 	}
 	is_test := dir.ends_with('_test.v')
-	is_script := dir.ends_with('.v')
+	is_script := dir.ends_with('.v') || dir.ends_with('.vsh')
 	if is_script && !os.file_exists(dir) {
 		println('`$dir` does not exist')
 		exit(1)
diff --git a/vlib/compiler/parser.v b/vlib/compiler/parser.v
index 54bfd13e42..03f83a8d1d 100644
--- a/vlib/compiler/parser.v
+++ b/vlib/compiler/parser.v
@@ -148,7 +148,11 @@ fn (v mut V) new_parser(scanner &Scanner, id string) Parser {
 		vroot: v.vroot
 		local_vars: [Var{}].repeat(MaxLocalVars)
 		import_table: v.table.get_file_import_table(id)
+		v_script: id.ends_with('.vsh')
 	}
+	if p.v_script {
+		println('new_parser: V script')
+	}	
 	$if js {
 		p.is_js = true
 	}
@@ -742,7 +746,7 @@ fn (p mut Parser) struct_decl() {
 		}
 		if p.tok == .key_mut {
 			if is_mut {
-				p.error('structs can only have one `mut:`, all private key_mut fields have to be grouped')
+				p.error('structs can only have one `mut:`, all private mutable fields have to be grouped')
 			}
 			is_mut = true
 			p.fmt_dec()
@@ -1928,23 +1932,17 @@ fn (p mut Parser) name_expr() string {
 		}
 		return typ
 	}
-	// Function (not method btw, methods are handled in dot())
-	mut f := p.table.find_fn(name) or {
-		// We are in the second pass, that means this function was not defined, throw an error.
+	// Function (not method btw, methods are handled in `dot()`)
+	mut f := p.table.find_fn_is_script(name, p.v_script) or {
+		// We are in the second pass, that means this function was not defined,
+		// throw an error.
 		if !p.first_pass() {
-			// V script? Try os module.
-			// TODO
-			if p.v_script {
-				//name = name.replace('main__', 'os__')
-				//f = p.table.find_fn(name)
-			}
 			// check for misspelled function / variable / module
 			suggested := p.identify_typo(name, p.import_table)
 			if suggested != '' {
 				p.error('undefined: `$name`. did you mean:$suggested')
 			}
 			// If orig_name is a mod, then printing undefined: `mod` tells us nothing
-			// if p.table.known_mod(orig_name) {
 			if p.table.known_mod(orig_name) || p.import_table.known_alias(orig_name) {
 				name = name.replace('__', '.')
 				p.error('undefined: `$name`')
@@ -1955,6 +1953,8 @@ fn (p mut Parser) name_expr() string {
 		} else {
 			p.next()
 			// First pass, the function can be defined later.
+			// Only in const definitions? (since fn bodies are skipped
+			// in the first pass).
 			return 'void'
 		}
 		return 'void'
@@ -3560,6 +3560,8 @@ fn (p mut Parser) for_st() {
 				typ: var_type
 				ptr: typ.contains('*')
 				is_changed: true
+				is_mut: false
+				is_for_var: true
 			})
 		}
 	} else {
diff --git a/vlib/compiler/table.v b/vlib/compiler/table.v
index 5acf8b3700..8f780b8ec0 100644
--- a/vlib/compiler/table.v
+++ b/vlib/compiler/table.v
@@ -105,6 +105,7 @@ mut:
 	is_moved        bool
 	line_nr         int
 	token_idx       int // this is a token index, which will be used by error reporting
+	is_for_var      bool
 }
 
 struct Type {
@@ -362,6 +363,22 @@ fn (t &Table) find_fn(name string) ?Fn {
 	return none
 }
 
+fn (t &Table) find_fn_is_script(name string, is_script bool) ?Fn {
+	mut f := t.fns[name]
+	if f.name.str != 0 { // TODO
+		return f
+	}
+	// V script? Try os module.
+	if is_script {
+		println('trying replace $name')
+		f = t.fns[name.replace('main__', 'os__')]
+		if f.name.str != 0 {
+			return f
+		}
+	}
+	return none
+}
+
 fn (t &Table) known_fn(name string) bool {
 	_ = t.find_fn(name) or { return false }
 	return true
diff --git a/vlib/os/os.v b/vlib/os/os.v
index df893b5274..c22c677a18 100644
--- a/vlib/os/os.v
+++ b/vlib/os/os.v
@@ -4,6 +4,8 @@
 
 module os
 
+import strings
+
 #include <sys/stat.h>
 #include <signal.h>
 #include <errno.h>
@@ -864,3 +866,14 @@ pub fn mkdir_all(path string) {
 		}
 	}
 }
+
+// TODO use []string.join once ...string becomes "[]string"
+pub fn join(base string, dirs ...string) string {
+	mut path := strings.new_builder(50)
+	path.write(base.trim_right('\\/'))
+	for d in dirs {
+		path.write(os.path_separator)
+		path.write(d)
+	}
+	return path.str()
+}