diff --git a/src/core/operations/ToCaseInsensitiveRegex.mjs b/src/core/operations/ToCaseInsensitiveRegex.mjs
index 044c350c..dcf0758b 100644
--- a/src/core/operations/ToCaseInsensitiveRegex.mjs
+++ b/src/core/operations/ToCaseInsensitiveRegex.mjs
@@ -50,37 +50,36 @@ class ToCaseInsensitiveRegex extends Operation {
             return result;
         }
 
+        // Example: [test] -> [[tT][eE][sS][tT]]
         input = preProcess(input);
 
-        // Example: [a-z] -> [a-zA-Z]
-        input = input.replace(/[a-z]-[a-z]/g, m => `${m}${m[0].toUpperCase()}-${m[2].toUpperCase()}`);
-
-        // Example: [a-z] -> [a-zA-Z]
-        input = input.replace(/[A-Z]-[A-Z]/g, m => `${m}${m[0].toLowerCase()}-${m[2].toLowerCase()}`);
+        // Example: [A-Z] -> [A-Za-z]
+        input = input.replace(/[A-Z]-[A-Z]/ig, m => `${m[0].toUpperCase()}-${m[2].toUpperCase()}${m[0].toLowerCase()}-${m[2].toLowerCase()}`);
 
         // Example: [H-d] -> [A-DH-dh-z]
         input = input.replace(/[A-Z]-[a-z]/g, m => `A-${m[2].toUpperCase()}${m}${m[0].toLowerCase()}-z`);
 
         // Example: [!-D] -> [!-Da-d]
-        input = input.replace(/[ -@]-[A-Z]/g, m => `${m}a-${m[2].toLowerCase()}`);
+        input = input.replace(/\\?[ -@]-[A-Z]/g, m => `${m}a-${m[2].toLowerCase()}`);
 
         // Example: [%-^] -> [%-^a-z]
-        input = input.replace(/[ -@]-[[-`]/g, m => `${m}a-z`);
+        input = input.replace(/\\?[ -@]-\\?[[-`]/g, m => `${m}a-z`);
 
         // Example: [K-`] -> [K-`k-z]
-        input = input.replace(/[A-Z]-[[-`]/g, m => `${m}${m[0].toLowerCase()}-z`);
+        input = input.replace(/[A-Z]-\\?[[-`]/g, m => `${m}${m[0].toLowerCase()}-z`);
 
         // Example: [[-}] -> [[-}A-Z]
-        input = input.replace(/[[-`]-[{-~]/g, m => `${m}A-Z`);
+        input = input.replace(/\\?[[-`]-\\?[{-~]/g, m => `${m}A-Z`);
 
         // Example: [b-}] -> [b-}B-Z]
-        input = input.replace(/[a-z]-[{-~]/g, m => `${m}${m[0].toUpperCase()}-Z`);
+        input = input.replace(/[a-z]-\\?[{-~]/g, m => `${m}${m[0].toUpperCase()}-Z`);
 
         // Example: [<-j] -> [<-z]
-        input = input.replace(/[ -@]-[a-z]/g, m => `${m[0]}-z`);
+        input = input.replace(/\\?[ -@]-[a-z]/g, m => `${m[0]}-z`);
 
         // Example: [^-j] -> [A-J^-j]
-        input = input.replace(/[[-`]-[a-z]/g, m => `A-${m[2].toUpperCase()}${m}`);
+        input = input.replace(/\\?[[-`]-[a-z]/g, m => `A-${m[2].toUpperCase()}${m}`);
+
         return input;
     }
 }