diff --git a/README.md b/README.md
index 0ac323d5e..0a77efb64 100644
--- a/README.md
+++ b/README.md
@@ -178,6 +178,8 @@ ss, err := arrutil.ToStrings([]int{1, 2}) // ss: []string{"1", "2"}
 func NewBuffer() *Buffer 
 // source at byteutil/byteutil.go
 func FirstLine(bs []byte) []byte 
+func StrOrErr(bs []byte, err error) (string, error) 
+func SafeString(bs []byte, err error) string 
 // source at byteutil/bytex.go
 func Md5(src any) []byte 
 // source at byteutil/encoder.go
@@ -1163,6 +1165,7 @@ func SplitInlineComment(val string) (string, string)
 func FirstLine(output string) string 
 // source at strutil/strutil.go
 func OrElse(s, newVal string) string 
+func Valid(ss ...string) string 
 func Replaces(str string, pairs map[string]string) string 
 func PrettyJSON(v any) (string, error) 
 func RenderTemplate(input string, data any, fns template.FuncMap, isFile ...bool) string 
diff --git a/README.zh-CN.md b/README.zh-CN.md
index f177e6d50..11f4d7478 100644
--- a/README.zh-CN.md
+++ b/README.zh-CN.md
@@ -177,6 +177,8 @@ ss, err := arrutil.ToStrings([]int{1, 2}) // ss: []string{"1", "2"}
 func NewBuffer() *Buffer 
 // source at byteutil/byteutil.go
 func FirstLine(bs []byte) []byte 
+func StrOrErr(bs []byte, err error) (string, error) 
+func SafeString(bs []byte, err error) string 
 // source at byteutil/bytex.go
 func Md5(src any) []byte 
 // source at byteutil/encoder.go
@@ -1164,6 +1166,7 @@ func SplitInlineComment(val string) (string, string)
 func FirstLine(output string) string 
 // source at strutil/strutil.go
 func OrElse(s, newVal string) string 
+func Valid(ss ...string) string 
 func Replaces(str string, pairs map[string]string) string 
 func PrettyJSON(v any) (string, error) 
 func RenderTemplate(input string, data any, fns template.FuncMap, isFile ...bool) string 
diff --git a/envutil/envutil_test.go b/envutil/envutil_test.go
index 86dec11a9..bbe91f06c 100644
--- a/envutil/envutil_test.go
+++ b/envutil/envutil_test.go
@@ -13,7 +13,7 @@ func TestParseEnvValue(t *testing.T) {
 		eKey, eVal, rVal, nVal string
 	}{
 		{"EnvKey", "EnvKey val", "${EnvKey}", "EnvKey val"},
-		{"EnvKey", "", "${EnvKey}", "${EnvKey}"},
+		{"EnvKey", "", "${EnvKey}", ""},
 		{"EnvKey0", "EnvKey0 val", "${ EnvKey0 }", "EnvKey0 val"},
 		{"EnvKey1", "EnvKey1 val", "${EnvKey1|defValue}", "EnvKey1 val"},
 		{"EnvKey1", "", "${EnvKey1|defValue}", "defValue"},
@@ -38,11 +38,12 @@ func TestParseEnvValue(t *testing.T) {
 	}
 
 	// test multi ENV key
-	rVal := "${FirstEnv}/${ SecondEnv }"
+	rVal := "${FirstEnv}/${ SecondEnv | def_val}"
 	is.Eq("", Getenv("FirstEnv"))
 	is.Eq("", Getenv("SecondEnv"))
-	is.Eq(rVal, ParseEnvValue(rVal))
-	is.Eq(rVal, VarParse(rVal))
+	is.Eq("/def_val", ParseEnvValue(rVal))
+	is.Eq("/def_val", VarParse(rVal))
+	is.Eq("/", VarReplace(rVal)) // use os.ExpandEnv()
 
 	testutil.MockEnvValues(map[string]string{
 		"FirstEnv":  "abc",
@@ -59,6 +60,6 @@ func TestParseEnvValue(t *testing.T) {
 	}, func() {
 		is.Eq("abc", Getenv("FirstEnv"))
 		is.Eq("", Getenv("SecondEnv"))
-		is.Eq("abc/${ SecondEnv }", ParseEnvValue(rVal))
+		is.Eq("abc/def_val", ParseEnvValue(rVal))
 	})
 }
diff --git a/strutil/value.go b/strutil/value.go
index 3ae2e87fd..73c31aa7b 100644
--- a/strutil/value.go
+++ b/strutil/value.go
@@ -15,79 +15,84 @@ func (s *Value) Set(val string) error {
 }
 
 // IsEmpty check
-func (s *Value) IsEmpty() bool {
-	return string(*s) == ""
+func (s Value) IsEmpty() bool {
+	return string(s) == ""
+}
+
+// IsBlank check
+func (s Value) IsBlank() bool {
+	return strings.TrimSpace(string(s)) == ""
 }
 
 // IsStartWith prefix
-func (s *Value) IsStartWith(sub string) bool {
-	return strings.HasPrefix(string(*s), sub)
+func (s Value) IsStartWith(sub string) bool {
+	return strings.HasPrefix(string(s), sub)
 }
 
 // HasPrefix prefix
-func (s *Value) HasPrefix(sub string) bool {
-	return strings.HasPrefix(string(*s), sub)
+func (s Value) HasPrefix(sub string) bool {
+	return strings.HasPrefix(string(s), sub)
 }
 
 // IsEndWith suffix
-func (s *Value) IsEndWith(sub string) bool {
-	return strings.HasSuffix(string(*s), sub)
+func (s Value) IsEndWith(sub string) bool {
+	return strings.HasSuffix(string(s), sub)
 }
 
 // HasSuffix suffix
-func (s *Value) HasSuffix(sub string) bool {
-	return strings.HasSuffix(string(*s), sub)
+func (s Value) HasSuffix(sub string) bool {
+	return strings.HasSuffix(string(s), sub)
 }
 
 // Bytes string to bytes
-func (s *Value) Bytes() []byte {
-	return []byte(*s)
+func (s Value) Bytes() []byte {
+	return []byte(s)
 }
 
 // Val string
-func (s *Value) Val() string {
-	return string(*s)
+func (s Value) Val() string {
+	return string(s)
 }
 
 // Int convert
-func (s *Value) Int() int {
-	return QuietInt(string(*s))
+func (s Value) Int() int {
+	return QuietInt(string(s))
 }
 
 // Int64 convert
-func (s *Value) Int64() int64 {
-	return QuietInt64(string(*s))
+func (s Value) Int64() int64 {
+	return QuietInt64(string(s))
 }
 
 // Bool convert
-func (s *Value) Bool() bool {
-	return QuietBool(string(*s))
+func (s Value) Bool() bool {
+	return QuietBool(string(s))
 }
 
 // Value string
-func (s *Value) String() string {
-	return string(*s)
+func (s Value) String() string {
+	return string(s)
 }
 
 // OrElse string
-func (s *Value) OrElse(or string) string {
-	if *s != "" {
-		return string(*s)
+func (s Value) OrElse(or string) string {
+	if s != "" {
+		return string(s)
 	}
 	return or
 }
 
 // Split string
-func (s *Value) Split(sep string) []string {
-	return strings.Split(string(*s), sep)
+func (s Value) Split(sep string) []string {
+	return strings.Split(string(s), sep)
 }
 
 // SplitN string
-func (s *Value) SplitN(sep string, n int) []string {
-	return strings.SplitN(string(*s), sep, n)
+func (s Value) SplitN(sep string, n int) []string {
+	return strings.SplitN(string(s), sep, n)
 }
 
-// TrimSpace string and return new
-func (s *Value) TrimSpace() Value {
-	return Value(strings.TrimSpace(string(*s)))
+// WithTrimSpace string and return new
+func (s Value) WithTrimSpace() Value {
+	return Value(strings.TrimSpace(string(s)))
 }
diff --git a/strutil/value_test.go b/strutil/value_test.go
index c7a057d64..a46ba11a0 100644
--- a/strutil/value_test.go
+++ b/strutil/value_test.go
@@ -13,12 +13,17 @@ func TestValue_usage(t *testing.T) {
 	assert.True(t, s.HasPrefix("abc"))
 	assert.True(t, s.IsEndWith("123"))
 	assert.True(t, s.HasSuffix("123"))
+	assert.False(t, s.IsEmpty())
+	assert.False(t, s.IsBlank())
 
 	assert.Eq(t, "abc-123", s.Val())
 	assert.Eq(t, "abc-123", s.String())
+	assert.Eq(t, "abc-123", s.OrElse("def"))
 
 	s1 := strutil.StrVal("abc-123")
 	assert.NotEmpty(t, s1.Val())
 	assert.Len(t, s1.Split("-"), 2)
 	assert.Len(t, s1.SplitN("-", 2), 2)
+
+	assert.Eq(t, "abc", strutil.Value(" abc ").WithTrimSpace().Val())
 }