Move internal modules to “internal” folder.

.internal/basePullAt.js

@@ -0,0 +1,35 @@
+import baseUnset from './.internal/baseUnset.js';
+import isIndex from './.internal/isIndex.js';
+
+/** Built-in value references. */
+const splice = Array.prototype.splice;
+
+/**
+ * The base implementation of `pullAt` without support for individual
+ * indexes or capturing the removed elements.
+ *
+ * @private
+ * @param {Array} array The array to modify.
+ * @param {number[]} indexes The indexes of elements to remove.
+ * @returns {Array} Returns `array`.
+ */
+function basePullAt(array, indexes) {
+  let length = array ? indexes.length : 0;
+  const lastIndex = length - 1;
+
+  while (length--) {
+    let previous;
+    const index = indexes[length];
+    if (length == lastIndex || index !== previous) {
+      previous = index;
+      if (isIndex(index)) {
+        splice.call(array, index, 1);
+      } else {
+        baseUnset(array, index);
+      }
+    }
+  }
+  return array;
+}
+
+export default basePullAt;