diff --git a/xplace/x.py b/xplace/x.py
index 9d6c584..8183a6b 100644
--- a/xplace/x.py
+++ b/xplace/x.py
@@ -21,16 +21,17 @@ parser = Lark(r'''
 
           ?unit : parens | brackets | char
    ?concat_func : unit
-                | concat_func "{" DIGITS "}"                     -> concat_repeat
-                | concat_func "?"                                -> zero_or_one
-                | concat_func "~"                                -> reverse
-                | concat_func "~" NUMBER                         -> roll
-                | concat_func "~{" NUMBER ["," DIGITS] "}"       -> roll
-                | concat_func "!"                                -> collapse
-                | concat_func "!" DIGIT+                         -> collapse
-                | concat_func "!{" numrange ("," numrange)* "}"  -> collapse_ranges
-                | concat_func "\\" DIGIT+                        -> index
-                | concat_func "\\{" numrange ("," numrange)* "}" -> index_ranges
+                | concat_func "{" DIGITS "}"                      -> concat_repeat
+                | concat_func "?"                                 -> zero_or_one
+                | concat_func "~"                                 -> reverse
+                | concat_func "~" NUMBER                          -> roll
+                | concat_func "~{" NUMBER ["," DIGITS] "}"        -> roll
+                | concat_func "!-"                                -> split
+                | concat_func "!"                                 -> collapse
+                | concat_func "\\-" DIGIT+                        -> negindex
+                | concat_func "\\-{" numrange ("," numrange)* "}" -> negindex_ranges
+                | concat_func "\\" DIGIT+                         -> index
+                | concat_func "\\{" numrange ("," numrange)* "}"  -> index_ranges
 
         ?concat : concat_func+
 
@@ -146,22 +147,23 @@ class Expand(Transformer):
                 result.append(x[i % len(x)])
         return result
 
+    def negindex(self, args):
+        x = args[0]
+        inds = set(int(i.value) % len(x) for i in args[1:])
+        inds = set(range(len(x))) - inds
+        return [x[i] for i in sorted(inds)]
+
+    def negindex_ranges(self, args):
+        x = args[0]
+        inds = set(i % len(x) for arg in args[1:] for i in arg)
+        inds = set(range(len(x))) - inds
+        return [x[i] for i in sorted(inds)]
+
+    def split(self, args):
+        return list(''.join(args[0]))
+
     def collapse(self, args):
-        result, x = '', args[0]
-        if len(args) > 1:
-            for i in args[1:]:
-                result += x[int(i.value) % len(x)]
-        else:
-            result = ''.join(args[0])
-        return [result]
-
-    def collapse_ranges(self, args):
-        result, x = '', args[0]
-        for arg in args[1:]:
-            for i in arg:
-                result += x[i % len(x)]
-        return [result]
-
+        return [''.join(args[0])]
 
     def concat_repeat(self, args):
         return self.concat([args[0]] * int(args[1].value))