diff --git a/include/internal/buffer/clip.h b/include/internal/buffer/clip.h
index 3f4a1a6..88ed46e 100644
--- a/include/internal/buffer/clip.h
+++ b/include/internal/buffer/clip.h
@@ -24,6 +24,7 @@ struct ClipBuffer : Buffer {
   void join(BEd &ctx, uint64_t start_line, uint64_t end_line) override;
   void remove(BEd &ctx, uint64_t start_line, uint64_t end_line) override;
   void append(BEd &ctx, vase::Shard *text, uint64_t line) override;
+  void replace(BEd &ctx, vase::Shard *text, uint64_t start_line, uint64_t end_line) override;
   void print(BEd &ctx, uint64_t start_line, uint64_t end_line) override;
   void number_print(BEd &ctx, uint64_t start_line, uint64_t end_line) override;
   void list_print(BEd &ctx, uint64_t start_line, uint64_t end_line) override;
diff --git a/include/internal/buffer/decl.h b/include/internal/buffer/decl.h
index f49572f..8ee6f39 100644
--- a/include/internal/buffer/decl.h
+++ b/include/internal/buffer/decl.h
@@ -43,6 +43,7 @@ struct Buffer {
   virtual void join(BEd &ctx, uint64_t start_line, uint64_t end_line) = 0;
   virtual void remove(BEd &ctx, uint64_t start_line, uint64_t end_line) = 0;
   virtual void append(BEd &ctx, vase::Shard *text, uint64_t line) = 0;
+  virtual void replace(BEd &ctx, vase::Shard *text, uint64_t start_line, uint64_t end_line) = 0;
   virtual void print(BEd &ctx, uint64_t start_line, uint64_t end_line) = 0;
   virtual void number_print(BEd &ctx, uint64_t start_line, uint64_t end_line) = 0;
   virtual void list_print(BEd &ctx, uint64_t start_line, uint64_t end_line) = 0;
diff --git a/include/internal/buffer/generic.h b/include/internal/buffer/generic.h
index a4a3758..78e0c75 100644
--- a/include/internal/buffer/generic.h
+++ b/include/internal/buffer/generic.h
@@ -28,6 +28,7 @@ struct GenericBuffer : Buffer {
   void join(BEd &ctx, uint64_t start_line, uint64_t end_line) override;
   void remove(BEd &ctx, uint64_t start_line, uint64_t end_line) override;
   void append(BEd &ctx, vase::Shard *text, uint64_t line) override;
+  void replace(BEd &ctx, vase::Shard *text, uint64_t start_line, uint64_t end_line) override;
   void print(BEd &ctx, uint64_t start_line, uint64_t end_line) override;
   void number_print(BEd &ctx, uint64_t start_line, uint64_t end_line) override;
   void list_print(BEd &ctx, uint64_t start_line, uint64_t end_line) override;
diff --git a/include/internal/marks/marks.h b/include/internal/marks/marks.h
index ddc5bd3..4c7b880 100644
--- a/include/internal/marks/marks.h
+++ b/include/internal/marks/marks.h
@@ -22,7 +22,7 @@ struct MarksEngine {
         continue;
       if (marks[i].number == UINT64_MAX)
         continue;
-      if (marks[i].number >= start)
+      if (marks[i].number > start)
         marks[i].number += count;
     }
   }
diff --git a/include/internal/vase/vase.h b/include/internal/vase/vase.h
index a8d190d..d9d6d87 100644
--- a/include/internal/vase/vase.h
+++ b/include/internal/vase/vase.h
@@ -48,6 +48,7 @@ std::string to_string(Shard *root, Range range);
 
 Shard *insert(AppendStorage *ap, Shard *root, Shard *text, uint64_t line);
 Shard *erase(Shard *root, uint64_t start, uint64_t end);
+Shard *replace(Shard *root, Shard *text, uint64_t start, uint64_t end);
 Shard *join(Shard *root, uint64_t start, uint64_t end);
 Shard *copy(Shard *root, uint64_t start, uint64_t end);
 void write_file(std::filesystem::path path, Shard *text);
diff --git a/src/internal/buffer/generic.cc b/src/internal/buffer/generic.cc
index 941137e..cc4390f 100644
--- a/src/internal/buffer/generic.cc
+++ b/src/internal/buffer/generic.cc
@@ -51,13 +51,15 @@ std::filesystem::path GenericBuffer::filename() {
 };
 
 void GenericBuffer::append(BEd &ctx, vase::Shard *text, uint64_t line) {
+  if (!text)
+    return;
   ctx.prev().buffername = name;
   ctx.prev().start = line + 1;
   ctx.prev().end = line + text->lines + 1;
   root = vase::insert(&ctx.append, root, text, line);
-  ctx.marks.insert(name, ctx.prev().start, ctx.prev().end);
+  ctx.marks.insert(name, line, text->lines + 1);
   if (parser)
-    parser->insert(root, ctx.prev().start, ctx.prev().end);
+    parser->insert(root, line, text->lines + 1);
   state = Modified;
 }
 
@@ -72,6 +74,33 @@ void GenericBuffer::remove(BEd &ctx, uint64_t start_line, uint64_t end_line) {
   state = Modified;
 }
 
+void GenericBuffer::replace(BEd &ctx, vase::Shard *text, uint64_t start_line, uint64_t end_line) {
+  if (!text) {
+    remove(ctx, start_line, end_line);
+    return;
+  }
+  ctx.prev().buffername = name;
+  ctx.prev().start = start_line;
+  ctx.prev().end = start_line + text->lines;
+  uint64_t new_count = text->lines + 1;
+  uint64_t old_count = end_line - start_line + 1;
+  root = vase::replace(root, text, start_line, end_line);
+  if (parser) {
+    parser->begin_edit();
+    parser->erase(start_line, old_count);
+    parser->insert(start_line, new_count);
+    parser->end_edit(root);
+  }
+  if (new_count > old_count) {
+    uint64_t diff = new_count - old_count;
+    ctx.marks.insert(name, end_line, diff);
+  } else if (new_count < old_count) {
+    uint64_t diff = old_count - new_count;
+    ctx.marks.collapse(name, start_line + new_count - 1, diff);
+  }
+  state = Modified;
+}
+
 void GenericBuffer::join(BEd &ctx, uint64_t start_line, uint64_t end_line) {
   root = vase::join(root, start_line, end_line);
   ctx.prev().buffername = name;
@@ -107,9 +136,9 @@ void GenericBuffer::substitute(
           parser->erase(line, old_lines);
       }
       if (new_lines) {
-        ctx.marks.insert(name, line, line + new_lines - 1);
+        ctx.marks.insert(name, line, line + new_lines);
         if (parser)
-          parser->insert(line, line + new_lines - 1);
+          parser->insert(line, new_lines);
       }
     }
   );
diff --git a/src/internal/buffer/special/clip.cc b/src/internal/buffer/special/clip.cc
index 7ae2c09..e3189a3 100644
--- a/src/internal/buffer/special/clip.cc
+++ b/src/internal/buffer/special/clip.cc
@@ -54,12 +54,12 @@ std::filesystem::path ClipBuffer::filename() {
 void ClipBuffer::append(BEd &ctx, vase::Shard *text, uint64_t line) {
   ctx.prev().buffername = name;
   ctx.prev().start = line + 1;
-  ctx.prev().end = line + text->lines + 1;
+  ctx.prev().end = line + (text ? text->lines + 1 : 0);
   auto s = vase::Shard::from_command("xclip -selection clipboard -o", true);
   s = vase::insert(&ctx.append, s, text, line);
   clip_write(s);
   vase::Shard::release(s);
-  ctx.marks.insert(name, ctx.prev().start, ctx.prev().end);
+  ctx.marks.insert(name, line, text->lines + 1);
 }
 
 void ClipBuffer::remove(BEd &ctx, uint64_t start_line, uint64_t end_line) {
@@ -73,6 +73,30 @@ void ClipBuffer::remove(BEd &ctx, uint64_t start_line, uint64_t end_line) {
   ctx.marks.erase(name, start_line, end_line - start_line + 1);
 }
 
+void ClipBuffer::replace(BEd &ctx, vase::Shard *text, uint64_t start_line, uint64_t end_line) {
+  if (!text) {
+    remove(ctx, start_line, end_line);
+    return;
+  }
+  ctx.prev().buffername = name;
+  ctx.prev().start = start_line;
+  ctx.prev().end = start_line + text->lines;
+  uint64_t new_count = text->lines + 1;
+  uint64_t old_count = end_line - start_line + 1;
+  auto s = vase::Shard::from_command("xclip -selection clipboard -o", true);
+  s = vase::replace(s, text, start_line, end_line);
+  clip_write(s);
+  vase::Shard::release(s);
+  if (new_count > old_count) {
+    uint64_t diff = new_count - old_count;
+    ctx.marks.insert(name, end_line, diff);
+  } else if (new_count < old_count) {
+    uint64_t diff = old_count - new_count;
+    ctx.marks.collapse(name, start_line + new_count - 1, diff);
+  }
+  state = Modified;
+}
+
 void ClipBuffer::join(BEd &ctx, uint64_t start_line, uint64_t end_line) {
   auto s = vase::Shard::from_command("xclip -selection clipboard -o", true);
   s = vase::join(s, start_line, end_line);
diff --git a/src/internal/functions/extended.cc b/src/internal/functions/extended.cc
index 4ccdc65..ec91b4a 100644
--- a/src/internal/functions/extended.cc
+++ b/src/internal/functions/extended.cc
@@ -14,7 +14,13 @@ void Function::register_extented(BEd &ctx) {
       .default_address = "",
       .accept_zero = false,
       .pre_text_mode = nullptr,
-      .handle = [](BEd &, const buffer::Address &, vase::Shard *, const Argument &arg_, std::vector<buffer::Line> *) {
+      .handle = [](
+                  BEd &,
+                  const buffer::Address &,
+                  vase::Shard *,
+                  const Argument &arg_,
+                  std::vector<buffer::Line> *
+                ) {
         auto path = std::get<std::string>(arg_);
         const auto first = path.find_first_not_of(" \t");
         const auto last = path.find_last_not_of(" \t");
@@ -46,7 +52,13 @@ void Function::register_extented(BEd &ctx) {
       .default_address = "",
       .accept_zero = false,
       .pre_text_mode = nullptr,
-      .handle = [](BEd &ctx, const buffer::Address &, vase::Shard *, const Argument &, std::vector<buffer::Line> *) {
+      .handle = [](
+                  BEd &ctx,
+                  const buffer::Address &,
+                  vase::Shard *,
+                  const Argument &,
+                  std::vector<buffer::Line> *
+                ) {
         char cwd[PATH_MAX];
         if (!getcwd(cwd, sizeof(cwd)))
           throw ed_error("Can't determine current directory.");
@@ -54,5 +66,36 @@ void Function::register_extented(BEd &ctx) {
       },
     }
   );
+  ctx.functions.insert(
+    "x",
+    Function{
+      .address_kind = Function::AddressKind::Range,
+      .argument_kind = Function::ArgumentKind::Range,
+      .input_mode = Function::InputMode::None,
+      .desc = "Exchange a range of lines for another.",
+      .default_address = ".,.",
+      .accept_zero = false,
+      .pre_text_mode = nullptr,
+      .handle = [](
+                  BEd &ctx,
+                  const buffer::Address &addr_,
+                  vase::Shard *,
+                  const Argument &arg_,
+                  std::vector<buffer::Line> *
+                ) {
+        auto addr = std::get<buffer::Range>(addr_);
+        auto arg = std::get<buffer::Range>(arg_);
+        auto text = ctx.buffer(addr.buffername).copy(addr.start, addr.end);
+        try {
+          ctx.buffer(arg.buffername).replace(ctx, text, arg.start, arg.end);
+          vase::Shard::release(text);
+        } catch (...) {
+          vase::Shard::release(text);
+          throw;
+        }
+        ctx.current() = {arg.buffername, arg.start + addr.end - addr.start + 1};
+      },
+    }
+  );
 }
 } // namespace bed::internal::functions
diff --git a/src/internal/functions/posix.cc b/src/internal/functions/posix.cc
index ac535b1..5411dc0 100644
--- a/src/internal/functions/posix.cc
+++ b/src/internal/functions/posix.cc
@@ -38,7 +38,13 @@ void Function::register_posix(BEd &ctx) {
       .default_address = ".",
       .accept_zero = true,
       .pre_text_mode = nullptr,
-      .handle = [](BEd &ctx, const buffer::Address &addr_, vase::Shard *text, const Argument &, std::vector<buffer::Line> *) {
+      .handle = [](
+                  BEd &ctx,
+                  const buffer::Address &addr_,
+                  vase::Shard *text,
+                  const Argument &,
+                  std::vector<buffer::Line> *
+                ) {
         auto addr = std::get<buffer::Line>(addr_);
         ctx.buffer(addr.buffername).append(ctx, text, addr.number);
         ctx.current() = {ctx.prev().buffername, ctx.prev().end};
@@ -56,10 +62,15 @@ void Function::register_posix(BEd &ctx) {
       .default_address = ".,.",
       .accept_zero = false,
       .pre_text_mode = nullptr,
-      .handle = [](BEd &ctx, const buffer::Address &addr_, vase::Shard *text, const Argument &, std::vector<buffer::Line> *) {
+      .handle = [](
+                  BEd &ctx,
+                  const buffer::Address &addr_,
+                  vase::Shard *text,
+                  const Argument &,
+                  std::vector<buffer::Line> *
+                ) {
         auto addr = std::get<buffer::Range>(addr_);
-        ctx.buffer(addr.buffername).remove(ctx, addr.start, addr.end);
-        ctx.buffer(addr.buffername).append(ctx, text, addr.start - 1);
+        ctx.buffer(addr.buffername).replace(ctx, text, addr.start, addr.end);
         ctx.current() = {ctx.prev().buffername, ctx.prev().end};
         vase::Shard::release(text);
       }
@@ -75,7 +86,13 @@ void Function::register_posix(BEd &ctx) {
       .default_address = ".,.",
       .accept_zero = false,
       .pre_text_mode = nullptr,
-      .handle = [](BEd &ctx, const buffer::Address &addr_, vase::Shard *, const Argument &, std::vector<buffer::Line> *) {
+      .handle = [](
+                  BEd &ctx,
+                  const buffer::Address &addr_,
+                  vase::Shard *,
+                  const Argument &,
+                  std::vector<buffer::Line> *
+                ) {
         auto addr = std::get<buffer::Range>(addr_);
         ctx.buffer(addr.buffername).remove(ctx, addr.start, addr.end);
         ctx.current() = {addr.buffername, addr.start};
@@ -92,7 +109,13 @@ void Function::register_posix(BEd &ctx) {
       .default_address = "",
       .accept_zero = false,
       .pre_text_mode = nullptr,
-      .handle = [](BEd &ctx, const buffer::Address &addr_, vase::Shard *, const Argument &arg, std::vector<buffer::Line> *) {
+      .handle = [](
+                  BEd &ctx,
+                  const buffer::Address &addr_,
+                  vase::Shard *,
+                  const Argument &arg,
+                  std::vector<buffer::Line> *
+                ) {
         auto &addr = std::get<std::string>(addr_);
         auto &buf = ctx.buffer(addr);
         if (buf.state == buffer::Buffer::Modified) {
@@ -136,7 +159,13 @@ void Function::register_posix(BEd &ctx) {
       .default_address = "",
       .accept_zero = false,
       .pre_text_mode = nullptr,
-      .handle = [](BEd &ctx, const buffer::Address &addr_, vase::Shard *, const Argument &arg, std::vector<buffer::Line> *) {
+      .handle = [](
+                  BEd &ctx,
+                  const buffer::Address &addr_,
+                  vase::Shard *,
+                  const Argument &arg,
+                  std::vector<buffer::Line> *
+                ) {
         auto &addr = std::get<std::string>(addr_);
         auto &buf = ctx.buffer(addr);
         vase::Shard *s = nullptr;
@@ -176,7 +205,13 @@ void Function::register_posix(BEd &ctx) {
       .default_address = "",
       .accept_zero = false,
       .pre_text_mode = nullptr,
-      .handle = [](BEd &ctx, const buffer::Address &addr_, vase::Shard *, const Argument &arg, std::vector<buffer::Line> *) {
+      .handle = [](
+                  BEd &ctx,
+                  const buffer::Address &addr_,
+                  vase::Shard *,
+                  const Argument &arg,
+                  std::vector<buffer::Line> *
+                ) {
         auto &addr = std::get<std::string>(addr_);
         auto &buf_ = ctx.buffer(addr);
         if (buf_.kind != buffer::Buffer::Kind::Generic)
@@ -202,7 +237,13 @@ void Function::register_posix(BEd &ctx) {
       .default_address = "",
       .accept_zero = false,
       .pre_text_mode = nullptr,
-      .handle = [](BEd &ctx, const buffer::Address &, vase::Shard *, const Argument &, std::vector<buffer::Line> *) {
+      .handle = [](
+                  BEd &ctx,
+                  const buffer::Address &,
+                  vase::Shard *,
+                  const Argument &,
+                  std::vector<buffer::Line> *
+                ) {
         ctx.io.write_line(ctx.last_help);
       }
     }
@@ -217,7 +258,13 @@ void Function::register_posix(BEd &ctx) {
       .default_address = "",
       .accept_zero = false,
       .pre_text_mode = nullptr,
-      .handle = [](BEd &ctx, const buffer::Address &, vase::Shard *, const Argument &, std::vector<buffer::Line> *) {
+      .handle = [](
+                  BEd &ctx,
+                  const buffer::Address &,
+                  vase::Shard *,
+                  const Argument &,
+                  std::vector<buffer::Line> *
+                ) {
         ctx.help_mode = !ctx.help_mode;
         if (ctx.help_mode)
           ctx.io.write_line(ctx.last_help);
@@ -234,7 +281,13 @@ void Function::register_posix(BEd &ctx) {
       .default_address = ".",
       .accept_zero = true,
       .pre_text_mode = nullptr,
-      .handle = [](BEd &ctx, const buffer::Address &addr_, vase::Shard *text, const Argument &, std::vector<buffer::Line> *) {
+      .handle = [](
+                  BEd &ctx,
+                  const buffer::Address &addr_,
+                  vase::Shard *text,
+                  const Argument &,
+                  std::vector<buffer::Line> *
+                ) {
         auto addr = std::get<buffer::Line>(addr_);
         if (addr.number)
           addr.number--;
@@ -254,7 +307,13 @@ void Function::register_posix(BEd &ctx) {
       .default_address = ".,.+1",
       .accept_zero = false,
       .pre_text_mode = nullptr,
-      .handle = [](BEd &ctx, const buffer::Address &addr_, vase::Shard *, const Argument &, std::vector<buffer::Line> *) {
+      .handle = [](
+                  BEd &ctx,
+                  const buffer::Address &addr_,
+                  vase::Shard *,
+                  const Argument &,
+                  std::vector<buffer::Line> *
+                ) {
         auto addr = std::get<buffer::Range>(addr_);
         ctx.buffer(addr.buffername).join(ctx, addr.start, addr.end);
         ctx.current() = {addr.buffername, addr.start};
@@ -271,7 +330,13 @@ void Function::register_posix(BEd &ctx) {
       .default_address = ".",
       .accept_zero = false,
       .pre_text_mode = nullptr,
-      .handle = [](BEd &ctx, const buffer::Address &addr_, vase::Shard *, const Argument &arg, std::vector<buffer::Line> *) {
+      .handle = [](
+                  BEd &ctx,
+                  const buffer::Address &addr_,
+                  vase::Shard *,
+                  const Argument &arg,
+                  std::vector<buffer::Line> *
+                ) {
         auto &addr = std::get<buffer::Line>(addr_);
         ctx.mark(std::get<char>(arg), addr);
       }
@@ -287,7 +352,13 @@ void Function::register_posix(BEd &ctx) {
       .default_address = ".,.",
       .accept_zero = false,
       .pre_text_mode = nullptr,
-      .handle = [](BEd &ctx, const buffer::Address &addr_, vase::Shard *, const Argument &, std::vector<buffer::Line> *) {
+      .handle = [](
+                  BEd &ctx,
+                  const buffer::Address &addr_,
+                  vase::Shard *,
+                  const Argument &,
+                  std::vector<buffer::Line> *
+                ) {
         auto addr = std::get<buffer::Range>(addr_);
         ctx.buffer(addr.buffername).list_print(ctx, addr.start, addr.end);
         ctx.current() = {addr.buffername, addr.end};
@@ -304,7 +375,13 @@ void Function::register_posix(BEd &ctx) {
       .default_address = ".,.",
       .accept_zero = false,
       .pre_text_mode = nullptr,
-      .handle = [](BEd &ctx, const buffer::Address &addr_, vase::Shard *, const Argument &arg_, std::vector<buffer::Line> *) {
+      .handle = [](
+                  BEd &ctx,
+                  const buffer::Address &addr_,
+                  vase::Shard *,
+                  const Argument &arg_,
+                  std::vector<buffer::Line> *
+                ) {
         auto addr = std::get<buffer::Range>(addr_);
         auto arg = std::get<buffer::Line>(arg_);
         if (arg.buffername == addr.buffername
@@ -343,7 +420,13 @@ void Function::register_posix(BEd &ctx) {
       .default_address = ".,.",
       .accept_zero = false,
       .pre_text_mode = nullptr,
-      .handle = [](BEd &ctx, const buffer::Address &addr_, vase::Shard *, const Argument &, std::vector<buffer::Line> *) {
+      .handle = [](
+                  BEd &ctx,
+                  const buffer::Address &addr_,
+                  vase::Shard *,
+                  const Argument &,
+                  std::vector<buffer::Line> *
+                ) {
         auto addr = std::get<buffer::Range>(addr_);
         ctx.buffer(addr.buffername).number_print(ctx, addr.start, addr.end);
         ctx.current() = {addr.buffername, addr.end};
@@ -360,7 +443,13 @@ void Function::register_posix(BEd &ctx) {
       .default_address = ".,.",
       .accept_zero = false,
       .pre_text_mode = nullptr,
-      .handle = [](BEd &ctx, const buffer::Address &addr_, vase::Shard *, const Argument &, std::vector<buffer::Line> *) {
+      .handle = [](
+                  BEd &ctx,
+                  const buffer::Address &addr_,
+                  vase::Shard *,
+                  const Argument &,
+                  std::vector<buffer::Line> *
+                ) {
         auto addr = std::get<buffer::Range>(addr_);
         ctx.buffer(addr.buffername).print(ctx, addr.start, addr.end);
         ctx.current() = {addr.buffername, addr.end};
@@ -377,7 +466,13 @@ void Function::register_posix(BEd &ctx) {
       .default_address = "",
       .accept_zero = false,
       .pre_text_mode = nullptr,
-      .handle = [](BEd &ctx, const buffer::Address &, vase::Shard *, const Argument &, std::vector<buffer::Line> *) {
+      .handle = [](
+                  BEd &ctx,
+                  const buffer::Address &,
+                  vase::Shard *,
+                  const Argument &,
+                  std::vector<buffer::Line> *
+                ) {
         ctx.prompt_mode = !ctx.prompt_mode;
         if (ctx.prompt_mode && !ctx.prompt) {
           ctx.prompt = [](BEd &) { return "*"; };
@@ -395,7 +490,13 @@ void Function::register_posix(BEd &ctx) {
       .default_address = "",
       .accept_zero = false,
       .pre_text_mode = nullptr,
-      .handle = [](BEd &ctx, const buffer::Address &, vase::Shard *, const Argument &, std::vector<buffer::Line> *) {
+      .handle = [](
+                  BEd &ctx,
+                  const buffer::Address &,
+                  vase::Shard *,
+                  const Argument &,
+                  std::vector<buffer::Line> *
+                ) {
         std::string modified_buffers;
         for (auto &[name, buffer] : ctx.buffers) {
           if (buffer->state == buffer::Buffer::Modified) {
@@ -420,7 +521,13 @@ void Function::register_posix(BEd &ctx) {
       .default_address = "",
       .accept_zero = false,
       .pre_text_mode = nullptr,
-      .handle = [](BEd &, const buffer::Address &, vase::Shard *, const Argument &, std::vector<buffer::Line> *) {
+      .handle = [](
+                  BEd &,
+                  const buffer::Address &,
+                  vase::Shard *,
+                  const Argument &,
+                  std::vector<buffer::Line> *
+                ) {
         throw fatal_error("Force Quitting", 0);
       }
     }
@@ -435,7 +542,13 @@ void Function::register_posix(BEd &ctx) {
       .default_address = "$",
       .accept_zero = true,
       .pre_text_mode = nullptr,
-      .handle = [](BEd &ctx, const buffer::Address &addr_, vase::Shard *, const Argument &arg, std::vector<buffer::Line> *) {
+      .handle = [](
+                  BEd &ctx,
+                  const buffer::Address &addr_,
+                  vase::Shard *,
+                  const Argument &arg,
+                  std::vector<buffer::Line> *
+                ) {
         auto &addr = std::get<buffer::Line>(addr_);
         auto &buf = ctx.buffer(addr.buffername);
         vase::Shard *s = nullptr;
@@ -476,7 +589,13 @@ void Function::register_posix(BEd &ctx) {
       .default_address = ".,.",
       .accept_zero = false,
       .pre_text_mode = nullptr,
-      .handle = [](BEd &ctx, const buffer::Address &addr_, vase::Shard *, const Argument &arg_, std::vector<buffer::Line> *) {
+      .handle = [](
+                  BEd &ctx,
+                  const buffer::Address &addr_,
+                  vase::Shard *,
+                  const Argument &arg_,
+                  std::vector<buffer::Line> *
+                ) {
         auto &addr = std::get<buffer::Range>(addr_);
         auto arg = std::get<RegexArg>(arg_);
         if (arg.expression == "")
@@ -509,7 +628,13 @@ void Function::register_posix(BEd &ctx) {
       .default_address = ".,.",
       .accept_zero = false,
       .pre_text_mode = nullptr,
-      .handle = [](BEd &ctx, const buffer::Address &addr_, vase::Shard *, const Argument &arg_, std::vector<buffer::Line> *) {
+      .handle = [](
+                  BEd &ctx,
+                  const buffer::Address &addr_,
+                  vase::Shard *,
+                  const Argument &arg_,
+                  std::vector<buffer::Line> *
+                ) {
         auto addr = std::get<buffer::Range>(addr_);
         auto arg = std::get<buffer::Line>(arg_);
         auto text = ctx.buffer(addr.buffername).copy(addr.start, addr.end);
@@ -517,11 +642,6 @@ void Function::register_posix(BEd &ctx) {
           ctx.buffer(arg.buffername).append(ctx, text, arg.number);
           vase::Shard::release(text);
         } catch (...) {
-          if (!addr.start) {
-            vase::Shard::release(text);
-            throw;
-          }
-          ctx.buffer(addr.buffername).append(ctx, text, --addr.start);
           vase::Shard::release(text);
           throw;
         }
@@ -539,7 +659,13 @@ void Function::register_posix(BEd &ctx) {
       .default_address = "0,$",
       .accept_zero = true,
       .pre_text_mode = nullptr,
-      .handle = [](BEd &ctx, const buffer::Address &addr_, vase::Shard *, const Argument &arg, std::vector<buffer::Line> *) {
+      .handle = [](
+                  BEd &ctx,
+                  const buffer::Address &addr_,
+                  vase::Shard *,
+                  const Argument &arg,
+                  std::vector<buffer::Line> *
+                ) {
         auto addr = std::get<buffer::Range>(addr_);
         auto &buf = ctx.buffer(addr.buffername);
         vase::Shard *text;
@@ -584,7 +710,13 @@ void Function::register_posix(BEd &ctx) {
       .default_address = "$",
       .accept_zero = true,
       .pre_text_mode = nullptr,
-      .handle = [](BEd &ctx, const buffer::Address &addr_, vase::Shard *, const Argument &, std::vector<buffer::Line> *) {
+      .handle = [](
+                  BEd &ctx,
+                  const buffer::Address &addr_,
+                  vase::Shard *,
+                  const Argument &,
+                  std::vector<buffer::Line> *
+                ) {
         auto &addr = std::get<buffer::Range>(addr_);
         if (addr.start == addr.end)
           ctx.io.write_line(std::format(":{}:{}", addr.buffername, addr.start));
@@ -604,7 +736,13 @@ void Function::register_posix(BEd &ctx) {
       .default_address = "",
       .accept_zero = false,
       .pre_text_mode = nullptr,
-      .handle = [](BEd &ctx, const buffer::Address &addr_, vase::Shard *, const Argument &arg_, std::vector<buffer::Line> *) {
+      .handle = [](
+                  BEd &ctx,
+                  const buffer::Address &addr_,
+                  vase::Shard *,
+                  const Argument &arg_,
+                  std::vector<buffer::Line> *
+                ) {
         auto &addr = std::get<std::string>(addr_);
         auto filename = ctx.buffer(addr).filename();
         auto &arg = std::get<ShellArg>(arg_);
@@ -624,7 +762,13 @@ void Function::register_posix(BEd &ctx) {
     .default_address = ".+1",
     .accept_zero = true,
     .pre_text_mode = nullptr,
-    .handle = [](BEd &ctx, const buffer::Address &addr_, vase::Shard *, const Argument &, std::vector<buffer::Line> *) {
+    .handle = [](
+                BEd &ctx,
+                const buffer::Address &addr_,
+                vase::Shard *,
+                const Argument &,
+                std::vector<buffer::Line> *
+              ) {
       auto addr = std::get<buffer::Line>(addr_);
       if (addr.number != 0)
         ctx.buffer(addr.buffername).print(ctx, addr.number, addr.number);
@@ -639,7 +783,13 @@ void Function::register_posix(BEd &ctx) {
     .default_address = "",
     .accept_zero = false,
     .pre_text_mode = nullptr,
-    .handle = [](BEd &ctx, const buffer::Address &, vase::Shard *, const Argument &, std::vector<buffer::Line> *) {
+    .handle = [](
+                BEd &ctx,
+                const buffer::Address &,
+                vase::Shard *,
+                const Argument &,
+                std::vector<buffer::Line> *
+              ) {
       std::string modified_buffers;
       for (auto &[name, buffer] : ctx.buffers) {
         if (buffer->state == buffer::Buffer::Modified) {
diff --git a/src/internal/ui/text_mode/text_mode.cc b/src/internal/ui/text_mode/text_mode.cc
index e615e32..69c27f2 100644
--- a/src/internal/ui/text_mode/text_mode.cc
+++ b/src/internal/ui/text_mode/text_mode.cc
@@ -123,9 +123,14 @@ std::pair<vase::Shard *, bool> TextMode::run() {
       cursor = cmd.size();
       running = false;
     }
+    if (cmd.size() == 2 && cmd.compare(0, 2, ".\n") == 0) {
+      cmd.clear();
+      cursor = 0;
+      running = false;
+    }
   }
 
-  size_t total_lines = 1 + std::count(cmd.begin(), cmd.end(), '\n');
+  size_t total_lines = cmd.size() ? 1 + std::count(cmd.begin(), cmd.end(), '\n') : 0;
   uint16_t last_row = start + total_lines;
   bed.io.move_cursor(last_row, 1);
   bed.io.write("\n", 1);
diff --git a/src/internal/vase/vase.cc b/src/internal/vase/vase.cc
index 41c5458..9765718 100644
--- a/src/internal/vase/vase.cc
+++ b/src/internal/vase/vase.cc
@@ -173,6 +173,8 @@ Shard *insert(AppendStorage *ap, Shard *root, Shard *text, uint64_t line) {
     Shard::retain(text);
     return text;
   }
+  if (!text)
+    return root;
   if (line > root->lines + 1)
     throw ed_error("line out of range");
   Shard::retain(text);
@@ -201,6 +203,34 @@ Shard *insert(AppendStorage *ap, Shard *root, Shard *text, uint64_t line) {
   return result;
 }
 
+Shard *replace(Shard *root, Shard *text, uint64_t start, uint64_t end) {
+  if (!start || !end)
+    throw ed_error("Invalid range.");
+  start--;
+  end--;
+  if (!root)
+    throw ed_error("line range out of bounds");
+  uint64_t line_count = root->lines + 1;
+  if (start > end || end >= line_count)
+    throw ed_error("line range out of bounds");
+  uint64_t start_offset = offset_of(root, start);
+  uint64_t end_offset =
+    (end + 1 == line_count)
+      ? root->length
+      : offset_of(root, end + 1) - 1;
+  auto [left, rest] = Shard::split(root, start_offset);
+  auto [middle, right] = Shard::split(rest, end_offset - start_offset);
+  Shard *a = Shard::concat(left, text);
+  Shard *new_root = Shard::concat(a, right);
+  Shard::release(left);
+  Shard::release(rest);
+  Shard::release(middle);
+  Shard::release(right);
+  Shard::release(a);
+  Shard::release(root);
+  return new_root;
+}
+
 Shard *erase(Shard *root, uint64_t start, uint64_t end) {
   if (!start || !end)
     throw ed_error("Invalid range.");