diff --git a/src/func/builtin.rs b/src/func/builtin.rs
index 4ab2f938..be09add4 100644
--- a/src/func/builtin.rs
+++ b/src/func/builtin.rs
@@ -48,6 +48,8 @@ fn is_numeric(type_id: TypeId) -> bool {
 }
 
 /// Build in common binary operator implementations to avoid the cost of calling a registered function.
+///
+/// The return function will be registered as a _method_, so the first parameter cannot be consumed.
 #[must_use]
 pub fn get_builtin_binary_op_fn(
     op: &str,
@@ -291,28 +293,6 @@ pub fn get_builtin_binary_op_fn(
         }
         if type1 == type2 {
             return match op {
-                "+" => Some(|_, args| {
-                    let blob1 = &*args[0].read_lock::<Blob>().expect(BUILTIN);
-                    let blob2 = &*args[1].read_lock::<Blob>().expect(BUILTIN);
-                    let result = if blob1.is_empty() {
-                        if blob2.is_empty() {
-                            Blob::new()
-                        } else {
-                            blob2.clone()
-                        }
-                    } else {
-                        if blob2.is_empty() {
-                            blob1.clone()
-                        } else {
-                            let mut blob = Blob::with_capacity(blob1.len() + blob2.len());
-                            blob.extend_from_slice(blob1);
-                            blob.extend_from_slice(blob2);
-                            blob
-                        }
-                    };
-
-                    Ok(Dynamic::from_blob(result)) // do not use result.into() because it'll convert into an Array
-                }),
                 "==" => Some(impl_op!(Blob == Blob)),
                 "!=" => Some(impl_op!(Blob != Blob)),
                 _ => None,
@@ -533,6 +513,8 @@ pub fn get_builtin_binary_op_fn(
 }
 
 /// Build in common operator assignment implementations to avoid the cost of calling a registered function.
+///
+/// The return function is registered as a _method_, so the first parameter cannot be consumed.
 #[must_use]
 pub fn get_builtin_op_assignment_fn(
     op: &str,
@@ -770,22 +752,31 @@ pub fn get_builtin_op_assignment_fn(
         };
     }
 
+    #[cfg(not(feature = "no_index"))]
+    if type1 == TypeId::of::<crate::Array>() {
+        use crate::packages::array_basic::array_functions::*;
+        use crate::Array;
+
+        return match op {
+            "+=" => Some(|_, args| {
+                let array2 = std::mem::take(args[1]).cast::<Array>();
+                let array1 = &mut *args[0].write_lock::<Array>().expect(BUILTIN);
+                Ok(append(array1, array2).into())
+            }),
+            _ => None,
+        };
+    }
+
     #[cfg(not(feature = "no_index"))]
     if type1 == TypeId::of::<crate::Blob>() {
+        use crate::packages::blob_basic::blob_functions::*;
         use crate::Blob;
 
         return match op {
             "+=" => Some(|_, args| {
                 let blob2 = std::mem::take(args[1]).cast::<Blob>();
-                let mut blob1 = args[0].write_lock::<Blob>().expect(BUILTIN);
-                if !blob2.is_empty() {
-                    if blob1.is_empty() {
-                        *blob1 = blob2;
-                    } else {
-                        blob1.extend_from_slice(&blob2);
-                    }
-                }
-                Ok(Dynamic::UNIT)
+                let blob1 = &mut *args[0].write_lock::<Blob>().expect(BUILTIN);
+                Ok(append(blob1, blob2).into())
             }),
             _ => None,
         };
diff --git a/src/packages/array_basic.rs b/src/packages/array_basic.rs
index 8b9476e8..10c5d7f9 100644
--- a/src/packages/array_basic.rs
+++ b/src/packages/array_basic.rs
@@ -24,7 +24,7 @@ def_package! {
 }
 
 #[export_module]
-mod array_functions {
+pub mod array_functions {
     #[rhai_fn(name = "len", get = "len", pure)]
     pub fn len(array: &mut Array) -> INT {
         array.len() as INT
@@ -33,26 +33,29 @@ mod array_functions {
     pub fn push(array: &mut Array, item: Dynamic) {
         array.push(item);
     }
-    #[rhai_fn(name = "append", name = "+=")]
-    pub fn append(array: &mut Array, y: Array) {
-        if !y.is_empty() {
-            if array.is_empty() {
-                *array = y;
+    #[rhai_fn(name = "append")]
+    pub fn append(array1: &mut Array, array2: Array) {
+        if !array2.is_empty() {
+            if array1.is_empty() {
+                *array1 = array2;
             } else {
-                array.extend(y);
+                array1.extend(array2);
             }
         }
     }
     #[rhai_fn(name = "+")]
-    pub fn concat(mut array: Array, y: Array) -> Array {
-        if !y.is_empty() {
-            if array.is_empty() {
-                array = y;
+    pub fn concat(array1: Array, array2: Array) -> Array {
+        if !array2.is_empty() {
+            if array1.is_empty() {
+                array2
             } else {
-                array.extend(y);
+                let mut array = array1;
+                array.extend(array2);
+                array
             }
+        } else {
+            array1
         }
-        array
     }
     pub fn insert(array: &mut Array, position: INT, item: Dynamic) {
         if array.is_empty() {
diff --git a/src/packages/blob_basic.rs b/src/packages/blob_basic.rs
index bc4e06cd..048b1226 100644
--- a/src/packages/blob_basic.rs
+++ b/src/packages/blob_basic.rs
@@ -26,7 +26,7 @@ def_package! {
 }
 
 #[export_module]
-mod blob_functions {
+pub mod blob_functions {
     pub const fn blob() -> Blob {
         Blob::new()
     }
@@ -64,12 +64,10 @@ mod blob_functions {
     pub fn len(blob: &mut Blob) -> INT {
         blob.len() as INT
     }
-    #[rhai_fn(name = "push")]
     pub fn push(blob: &mut Blob, item: INT) {
         let item = (item & 0x000000ff) as u8;
         blob.push(item);
     }
-    #[rhai_fn(name = "append")]
     pub fn append(blob: &mut Blob, y: Blob) {
         if !y.is_empty() {
             if blob.is_empty() {
@@ -79,6 +77,20 @@ mod blob_functions {
             }
         }
     }
+    #[rhai_fn(name = "+")]
+    pub fn concat(blob1: Blob, blob2: Blob) -> Blob {
+        if !blob2.is_empty() {
+            if blob1.is_empty() {
+                blob2
+            } else {
+                let mut blob = blob1;
+                blob.extend(blob2);
+                blob
+            }
+        } else {
+            blob1
+        }
+    }
     pub fn insert(blob: &mut Blob, position: INT, item: INT) {
         let item = (item & 0x000000ff) as u8;
 
diff --git a/src/packages/mod.rs b/src/packages/mod.rs
index d1cd4d02..7f73e774 100644
--- a/src/packages/mod.rs
+++ b/src/packages/mod.rs
@@ -3,8 +3,8 @@
 use crate::{Module, Shared};
 
 pub(crate) mod arithmetic;
-mod array_basic;
-mod blob_basic;
+pub(crate) mod array_basic;
+pub(crate) mod blob_basic;
 mod fn_basic;
 mod iter_basic;
 mod lang_core;