diff --git a/README.md b/README.md
index 7448d3d..9421533 100644
--- a/README.md
+++ b/README.md
@@ -214,12 +214,12 @@ This crate offers a set of builtin functions.
 |------------|-----------------|-------------|
 | min | >= 1 | Returns the minimum of the arguments |
 | max | >= 1 | Returns the maximum of the arguments |
-| to_lowercase | 1 | Returns lower-case version of string |
 | len | 1 | Return the character length of string argument |
-| regex_matches | 2 | Returns true if first string argument matches regex in second |
-| regex_replace | 3 | Returns string with matches replaced by third argument |
-| trim | 1 | Strips whitespace from start and end of string |
-| to_uppercase | 1 | Returns upper-case version of string |
+| str::regex_matches | 2 | Returns true if first string argument matches regex in second |
+| str::regex_replace | 3 | Returns string with matches replaced by third argument |
+| str::to_lowercase | 1 | Returns lower-case version of string |
+| str::to_uppercase | 1 | Returns upper-case version of string |
+| str::trim | 1 | Strips whitespace from start and end of string |
 
 The `min` and `max` functions can deal with a mixture of integer and floating point arguments.
 They return the result as the type it was passed into the function. The regex functions require
diff --git a/src/function/builtin.rs b/src/function/builtin.rs
index 38ccb56..717b7db 100644
--- a/src/function/builtin.rs
+++ b/src/function/builtin.rs
@@ -58,15 +58,6 @@ pub fn builtin_function(identifier: &str) -> Option<Function> {
             }),
         )),
 
-        // string functions
-
-        "to_lowercase" => Some(Function::new(
-            Some(1),
-            Box::new(|arguments| {
-                let subject = expect_string(&arguments[0])?;
-                Ok(Value::from(subject.to_lowercase()))
-            }),
-        )),
         "len" => Some(Function::new(
             Some(1),
             Box::new(|arguments| {
@@ -74,8 +65,11 @@ pub fn builtin_function(identifier: &str) -> Option<Function> {
                 Ok(Value::from(subject.len() as i64))
             }),
         )),
+
+        // string functions
+
         #[cfg(feature = "regex_support")]
-        "regex_matches" => Some(Function::new(
+        "str::regex_matches" => Some(Function::new(
             Some(2),
             Box::new(|arguments| {
                 let subject = expect_string(&arguments[0])?;
@@ -87,7 +81,7 @@ pub fn builtin_function(identifier: &str) -> Option<Function> {
             }),
         )),
         #[cfg(feature = "regex_support")]
-        "regex_replace" => Some(Function::new(
+        "str::regex_replace" => Some(Function::new(
             Some(3),
             Box::new(|arguments| {
                 let subject = expect_string(&arguments[0])?;
@@ -99,20 +93,27 @@ pub fn builtin_function(identifier: &str) -> Option<Function> {
                 }
             }),
         )),
-        "trim" => Some(Function::new(
+        "str::to_lowercase" => Some(Function::new(
             Some(1),
             Box::new(|arguments| {
                 let subject = expect_string(&arguments[0])?;
-                Ok(Value::from(subject.trim()))
+                Ok(Value::from(subject.to_lowercase()))
             }),
         )),
-        "to_uppercase" => Some(Function::new(
+        "str::to_uppercase" => Some(Function::new(
             Some(1),
             Box::new(|arguments| {
                 let subject = expect_string(&arguments[0])?;
                 Ok(Value::from(subject.to_uppercase()))
             }),
         )),
+        "str::trim" => Some(Function::new(
+            Some(1),
+            Box::new(|arguments| {
+                let subject = expect_string(&arguments[0])?;
+                Ok(Value::from(subject.trim()))
+            }),
+        )),
         _ => None,
     }
 }
diff --git a/tests/integration.rs b/tests/integration.rs
index 6d308b7..2c90c9f 100644
--- a/tests/integration.rs
+++ b/tests/integration.rs
@@ -287,36 +287,36 @@ fn test_builtin_functions() {
         eval("max(4.0, 3)"),
         Ok(Value::Float(4.0))
     );
-    assert_eq!(
-        eval("to_lowercase(\"FOOBAR\")"),
-        Ok(Value::from("foobar"))
-    );
     assert_eq!(
         eval("len(\"foobar\")"),
         Ok(Value::Int(6))
     );
     assert_eq!(
-        eval("trim(\"  foo  bar \")"),
-        Ok(Value::from("foo  bar"))
+        eval("str::to_lowercase(\"FOOBAR\")"),
+        Ok(Value::from("foobar"))
     );
     assert_eq!(
-        eval("to_uppercase(\"foobar\")"),
+        eval("str::to_uppercase(\"foobar\")"),
         Ok(Value::from("FOOBAR"))
     );
+    assert_eq!(
+        eval("str::trim(\"  foo  bar \")"),
+        Ok(Value::from("foo  bar"))
+    );
 }
 
 #[test]
 #[cfg(feature = "regex_support")]
 fn test_regex_functions() {
     assert_eq!(
-        eval("regex_matches(\"foobar\", \"[ob]{3}\")"),
+        eval("str::regex_matches(\"foobar\", \"[ob]{3}\")"),
         Ok(Value::Boolean(true))
     );
     assert_eq!(
-        eval("regex_matches(\"gazonk\", \"[ob]{3}\")"),
+        eval("str::regex_matches(\"gazonk\", \"[ob]{3}\")"),
         Ok(Value::Boolean(false))
     );
-    match eval("regex_matches(\"foo\", \"[\")") {
+    match eval("str::regex_matches(\"foo\", \"[\")") {
         Err(EvalexprError::InvalidRegex{ regex, message }) => {
             assert_eq!(regex, "[");
             assert!(message.contains("unclosed character class"));
@@ -324,11 +324,11 @@ fn test_regex_functions() {
         v => panic!(v),
     };
     assert_eq!(
-        eval("regex_replace(\"foobar\", \".*?(o+)\", \"b$1\")"),
+        eval("str::regex_replace(\"foobar\", \".*?(o+)\", \"b$1\")"),
         Ok(Value::String("boobar".to_owned()))
     );
     assert_eq!(
-        eval("regex_replace(\"foobar\", \".*?(i+)\", \"b$1\")"),
+        eval("str::regex_replace(\"foobar\", \".*?(i+)\", \"b$1\")"),
         Ok(Value::String("foobar".to_owned()))
     );
 }