diff --git a/include/internal/buffer/types/generic.h b/include/internal/buffer/types/generic.h
index bc99cc6..a0aa133 100644
--- a/include/internal/buffer/types/generic.h
+++ b/include/internal/buffer/types/generic.h
@@ -29,7 +29,7 @@ struct GenericBuffer : ShardBuffer {
   void snapshot(std::string action);
   bool undo(BEd &ctx);
   bool redo(BEd &ctx);
-  void prune(int = 0);
+  uint64_t prune(int);
   bool waste() override;
   void load(BEd &ctx, vase::Shard *text) override;
   void set_filename(std::filesystem::path path) override;
diff --git a/src/bed/run.cc b/src/bed/run.cc
index eb7fac0..7686f61 100644
--- a/src/bed/run.cc
+++ b/src/bed/run.cc
@@ -174,7 +174,7 @@ internal::buffer::Buffer &BEd::buffer(const std::string &name) {
   if (name.starts_with(prefix)) {
     std::string_view path{name};
     path.remove_prefix(prefix.size());
-    auto slash = path.rfind('/');
+    auto slash = path.rfind('_');
     if (slash == std::string_view::npos || slash == 0 || slash == path.size() - 1)
       throw ed_error("invalid history");
     std::string bufname(path.substr(0, slash));
@@ -197,6 +197,15 @@ internal::buffer::Buffer &BEd::buffer(const std::string &name) {
     }
     throw ed_error("Buffer has no history.");
   }
+  for (auto &c : name)
+    if (!(('0' <= c && c <= '9')
+          || ('a' <= c && c <= 'z')
+          || ('A' <= c && c <= 'Z')
+          || c == '-' || c == '_'
+          || c == '+' || c == '.'
+          || c == ',' || c == '$'
+          || c == '/' || c == '~'))
+      throw ed_error("Invalid buffer name.");
   auto *buf = new internal::buffer::GenericBuffer(name);
   buffers.emplace(name, buf);
   return *buf;
diff --git a/src/internal/buffer/generic.cc b/src/internal/buffer/generic.cc
index 7a822e4..8815078 100644
--- a/src/internal/buffer/generic.cc
+++ b/src/internal/buffer/generic.cc
@@ -178,7 +178,7 @@ bool GenericBuffer::redo(BEd &ctx) {
   return true;
 }
 
-void GenericBuffer::prune(int keep) {
+uint64_t GenericBuffer::prune(int keep) {
   size_t drop =
     undo_stack.size() > (size_t)keep
       ? undo_stack.size() - keep
@@ -197,11 +197,13 @@ void GenericBuffer::prune(int keep) {
     vase::Shard::release(item.text);
   }
   redo_stack.clear();
+  return undo_stack.size();
 }
 
 bool GenericBuffer::waste() {
   return save_path.empty()
-         && root == nullptr;
+         && root == nullptr
+         && undo_stack.empty();
 }
 
 void GenericBuffer::load(BEd &ctx, vase::Shard *text) {
diff --git a/src/internal/buffer/special/clip.cc b/src/internal/buffer/special/clip.cc
index ea60171..afa9e68 100644
--- a/src/internal/buffer/special/clip.cc
+++ b/src/internal/buffer/special/clip.cc
@@ -128,7 +128,7 @@ void ClipBuffer::substitute(
       if (old_lines)
         ctx.marks.erase(name, line, old_lines);
       if (new_lines)
-        ctx.marks.insert(name, line, new_lines - 1);
+        ctx.marks.insert(name, line, new_lines);
     }
   );
   clip_write(s);
diff --git a/src/internal/functions/extended.cc b/src/internal/functions/extended.cc
index c0795e9..c554716 100644
--- a/src/internal/functions/extended.cc
+++ b/src/internal/functions/extended.cc
@@ -3,14 +3,134 @@
 #include "internal/functions/suffixes.h"
 
 namespace bed::internal::functions {
+namespace ansi {
+constexpr auto reset = "\033[0m";
+constexpr auto bold = "\033[1m";
+constexpr auto cyan = "\033[36m";
+constexpr auto yellow = "\033[33m";
+constexpr auto magenta = "\033[35m";
+constexpr auto green = "\033[32m";
+constexpr auto blue = "\033[34m";
+} // namespace ansi
+
+static void append_field(std::string &msg, std::string_view label, std::string_view label_color, std::string_view value) {
+  if (value.empty())
+    return;
+  msg += "\n";
+  msg += ansi::bold;
+  msg += label_color;
+  msg += label;
+  msg += ansi::reset;
+  msg += ": ";
+  msg += value;
+}
+
+static std::string_view address_kind_str(Function::AddressKind k) {
+  switch (k) {
+  case Function::AddressKind::None:
+    return "none";
+  case Function::AddressKind::Line:
+    return "1 line";
+  case Function::AddressKind::Range:
+    return "range";
+  }
+  return "";
+}
+
+static std::string_view input_mode_str(Function::InputMode m) {
+  switch (m) {
+  case Function::InputMode::None:
+    return "";
+  case Function::InputMode::Text:
+    return "text";
+  case Function::InputMode::Interactive:
+    return "interactive";
+  case Function::InputMode::CommandList:
+    return "command list";
+  }
+  return "";
+}
+
+static std::string_view argument_kind_str(Function::ArgumentKind a) {
+  switch (a) {
+  case Function::ArgumentKind::None:
+    return "";
+  case Function::ArgumentKind::Regex:
+    return "regex";
+  case Function::ArgumentKind::Shell:
+    return "shell command";
+  case Function::ArgumentKind::Any:
+    return "any";
+  case Function::ArgumentKind::File:
+    return "file";
+  case Function::ArgumentKind::Global:
+    return "ed global-style";
+  case Function::ArgumentKind::Mark:
+    return "mark name";
+  case Function::ArgumentKind::Number:
+    return "number";
+  case Function::ArgumentKind::Line:
+    return "address";
+  case Function::ArgumentKind::Range:
+    return "range";
+  case Function::ArgumentKind::Ruby:
+    return "ruby code";
+  }
+  return "";
+}
+
+static std::string describe_function(const Function &func) {
+  std::string msg = ansi::bold;
+  msg += func.desc;
+  msg += ansi::reset;
+  append_field(msg, "Default address", ansi::cyan, func.default_address);
+  append_field(msg, "Address", ansi::yellow, address_kind_str(func.address_kind));
+  if (func.accept_zero)
+    append_field(msg, "Zero address", ansi::magenta, "allowed");
+  append_field(msg, "Input", ansi::green, input_mode_str(func.input_mode));
+  append_field(msg, "Argument", ansi::blue, argument_kind_str(func.argument_kind));
+  return msg;
+}
+
 void Function::register_extented(BEd &ctx) {
+  ctx.functions.insert(
+    "*",
+    Function{
+      .address_kind = Function::AddressKind::None,
+      .argument_kind = Function::ArgumentKind::Any,
+      .input_mode = Function::InputMode::None,
+      .desc = "Explain a command",
+      .default_address = "",
+      .accept_zero = false,
+      .pre_text_mode = nullptr,
+      .handle = [](
+                  BEd &ctx,
+                  const buffer::Address &,
+                  vase::Shard *,
+                  const Argument &arg_,
+                  std::vector<buffer::Line> *
+                ) {
+        auto &str = std::get<std::string>(arg_);
+        if (str.empty()) {
+          ctx.io.write_line(describe_function(ctx.no_op));
+          return;
+        }
+        auto len = ctx.functions.longest_match(str);
+        if (len == str.size()) {
+          ctx.io.write_line(describe_function(*ctx.functions.get_ptr(str)));
+          return;
+        }
+        throw ed_error("Not a valid function name.");
+      },
+    }
+  );
   ctx.functions.insert(
     "#",
     Function{
       .address_kind = Function::AddressKind::None,
       .argument_kind = Function::ArgumentKind::Any,
       .input_mode = Function::InputMode::None,
-      .desc = "Comment.",
+      .desc = "Write a comment",
       .default_address = "",
       .accept_zero = false,
       .pre_text_mode = nullptr,
@@ -29,7 +149,7 @@ void Function::register_extented(BEd &ctx) {
       .address_kind = Function::AddressKind::Range,
       .argument_kind = Function::ArgumentKind::Any,
       .input_mode = Function::InputMode::None,
-      .desc = "Echo given message.",
+      .desc = "Echo the given message (replacing $1-$4 with address information)",
       .default_address = "",
       .accept_zero = true,
       .pre_text_mode = nullptr,
@@ -57,17 +177,30 @@ void Function::register_extented(BEd &ctx) {
               str[i - 1] = '\n';
             continue;
           }
-          if (str[i] == '$' && i < str.size() && '1' <= str[i + 1] && str[i + 1] <= '2') {
-            bool one = str[i + 1] == '1';
+          if (str[i] == '$' && i < str.size() && '1' <= str[i + 1] && str[i + 1] <= '4') {
+            char c = str[i + 1];
             str.erase(i, 2);
-            if (one) {
+            switch (c) {
+            case '1': {
               auto start = std::to_string(addr.start);
               str.insert(i, start);
               i += start.size();
-            } else {
+            } break;
+            case '2': {
               auto end = std::to_string(addr.end);
               str.insert(i, end);
               i += end.size();
+            } break;
+            case '3': {
+              str.insert(i, addr.buffername);
+              i += addr.buffername.size();
+            } break;
+            case '4': {
+              auto &buf = ctx.buffer(addr.buffername);
+              auto filename = buf.filename().string();
+              str.insert(i, filename);
+              i += filename.size();
+            } break;
             }
             continue;
           }
@@ -83,7 +216,7 @@ void Function::register_extented(BEd &ctx) {
       .address_kind = Function::AddressKind::None,
       .argument_kind = Function::ArgumentKind::Any,
       .input_mode = Function::InputMode::None,
-      .desc = "Change directory.",
+      .desc = "Change directory",
       .default_address = "",
       .accept_zero = false,
       .pre_text_mode = nullptr,
@@ -121,7 +254,7 @@ void Function::register_extented(BEd &ctx) {
       .address_kind = Function::AddressKind::None,
       .argument_kind = Function::ArgumentKind::None,
       .input_mode = Function::InputMode::None,
-      .desc = "Print directory.",
+      .desc = "Print the current working directory",
       .default_address = "",
       .accept_zero = false,
       .pre_text_mode = nullptr,
@@ -145,7 +278,7 @@ void Function::register_extented(BEd &ctx) {
       .address_kind = Function::AddressKind::Range,
       .argument_kind = Function::ArgumentKind::Range,
       .input_mode = Function::InputMode::None,
-      .desc = "Exchange a range of lines for another.",
+      .desc = "Exchange a range of lines for another",
       .default_address = ".,.",
       .accept_zero = false,
       .pre_text_mode = nullptr,
@@ -175,7 +308,7 @@ void Function::register_extented(BEd &ctx) {
       .address_kind = Function::AddressKind::None,
       .argument_kind = Function::ArgumentKind::None,
       .input_mode = Function::InputMode::None,
-      .desc = "Redo last undo.",
+      .desc = "Redo the last undo modification",
       .default_address = "",
       .accept_zero = false,
       .pre_text_mode = nullptr,
@@ -202,7 +335,7 @@ void Function::register_extented(BEd &ctx) {
       .address_kind = Function::AddressKind::None,
       .argument_kind = Function::ArgumentKind::None,
       .input_mode = Function::InputMode::None,
-      .desc = "List history versions.",
+      .desc = "List available history versions",
       .default_address = "",
       .accept_zero = false,
       .pre_text_mode = nullptr,
@@ -222,5 +355,34 @@ void Function::register_extented(BEd &ctx) {
       }
     }
   );
+  ctx.functions.insert(
+    "hp",
+    Function{
+      .address_kind = Function::AddressKind::None,
+      .argument_kind = Function::ArgumentKind::Number,
+      .input_mode = Function::InputMode::None,
+      .desc = "Prune old history versions",
+      .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<std::string>(addr_);
+        auto &arg = std::get<int64_t>(arg_);
+        auto &buf_ = ctx.buffer(addr);
+        if (buf_.kind != buffer::Buffer::Kind::Generic)
+          throw ed_error("Can't prune buffer.");
+        auto &buf = *(buffer::GenericBuffer *)&buf_;
+        auto versions = buf.prune(arg);
+        if (!ctx.suppress_mode)
+          ctx.io.write_line(std::format("{} undo versions left.", versions));
+      }
+    }
+  );
 }
 } // namespace bed::internal::functions
diff --git a/src/internal/functions/posix.cc b/src/internal/functions/posix.cc
index 02b917a..b1fca20 100644
--- a/src/internal/functions/posix.cc
+++ b/src/internal/functions/posix.cc
@@ -34,7 +34,7 @@ void Function::register_posix(BEd &ctx) {
       .address_kind = Function::AddressKind::Line,
       .argument_kind = Function::ArgumentKind::None,
       .input_mode = Function::InputMode::Text,
-      .desc = "Append text to a line.",
+      .desc = "Append text to a line",
       .default_address = ".",
       .accept_zero = true,
       .pre_text_mode = nullptr,
@@ -57,7 +57,7 @@ void Function::register_posix(BEd &ctx) {
       .address_kind = Function::AddressKind::Range,
       .argument_kind = Function::ArgumentKind::None,
       .input_mode = Function::InputMode::Text,
-      .desc = "Change set of lines.",
+      .desc = "Change a range of lines",
       .default_address = ".,.",
       .accept_zero = false,
       .pre_text_mode = nullptr,
@@ -80,7 +80,7 @@ void Function::register_posix(BEd &ctx) {
       .address_kind = Function::AddressKind::Range,
       .argument_kind = Function::ArgumentKind::None,
       .input_mode = Function::InputMode::None,
-      .desc = "Delete set of lines.",
+      .desc = "Delete a range of lines",
       .default_address = ".,.",
       .accept_zero = false,
       .pre_text_mode = nullptr,
@@ -102,7 +102,7 @@ void Function::register_posix(BEd &ctx) {
       .address_kind = Function::AddressKind::None,
       .argument_kind = Function::ArgumentKind::File,
       .input_mode = Function::InputMode::None,
-      .desc = "Try load a file into the current buffer.",
+      .desc = "Load a file into the current buffer, warn once if unsaved changes exist",
       .default_address = "",
       .accept_zero = false,
       .pre_text_mode = nullptr,
@@ -152,7 +152,7 @@ void Function::register_posix(BEd &ctx) {
       .address_kind = Function::AddressKind::None,
       .argument_kind = Function::ArgumentKind::File,
       .input_mode = Function::InputMode::None,
-      .desc = "Load a file into the current buffer.",
+      .desc = "Load a file into the current buffer, discarding unsaved changes",
       .default_address = "",
       .accept_zero = false,
       .pre_text_mode = nullptr,
@@ -198,7 +198,7 @@ void Function::register_posix(BEd &ctx) {
       .address_kind = Function::AddressKind::None,
       .argument_kind = Function::ArgumentKind::File,
       .input_mode = Function::InputMode::None,
-      .desc = "Set a save path.",
+      .desc = "Set/print a save path",
       .default_address = "",
       .accept_zero = false,
       .pre_text_mode = nullptr,
@@ -248,7 +248,7 @@ void Function::register_posix(BEd &ctx) {
       .address_kind = Function::AddressKind::None,
       .argument_kind = Function::ArgumentKind::None,
       .input_mode = Function::InputMode::None,
-      .desc = "Toggle help mode.",
+      .desc = "Toggle help mode",
       .default_address = "",
       .accept_zero = false,
       .pre_text_mode = nullptr,
@@ -271,7 +271,7 @@ void Function::register_posix(BEd &ctx) {
       .address_kind = Function::AddressKind::Line,
       .argument_kind = Function::ArgumentKind::None,
       .input_mode = Function::InputMode::Text,
-      .desc = "Insert text before a line.",
+      .desc = "Insert text before a line",
       .default_address = ".",
       .accept_zero = true,
       .pre_text_mode = nullptr,
@@ -296,7 +296,7 @@ void Function::register_posix(BEd &ctx) {
       .address_kind = Function::AddressKind::Range,
       .argument_kind = Function::ArgumentKind::None,
       .input_mode = Function::InputMode::None,
-      .desc = "Join a set of lines.",
+      .desc = "Join a range of lines",
       .default_address = ".,.+1",
       .accept_zero = false,
       .pre_text_mode = nullptr,
@@ -318,7 +318,7 @@ void Function::register_posix(BEd &ctx) {
       .address_kind = Function::AddressKind::Line,
       .argument_kind = Function::ArgumentKind::Mark,
       .input_mode = Function::InputMode::None,
-      .desc = "Mark a line.",
+      .desc = "Mark a line",
       .default_address = ".",
       .accept_zero = false,
       .pre_text_mode = nullptr,
@@ -340,7 +340,7 @@ void Function::register_posix(BEd &ctx) {
       .address_kind = Function::AddressKind::Range,
       .argument_kind = Function::ArgumentKind::None,
       .input_mode = Function::InputMode::None,
-      .desc = "List (print unambiguous) range",
+      .desc = "Print a range, showing nonprinting characters unambiguously",
       .default_address = ".,.",
       .accept_zero = false,
       .pre_text_mode = nullptr,
@@ -363,7 +363,7 @@ void Function::register_posix(BEd &ctx) {
       .address_kind = Function::AddressKind::Range,
       .argument_kind = Function::ArgumentKind::Line,
       .input_mode = Function::InputMode::None,
-      .desc = "Move a range of lines.",
+      .desc = "Move a range of lines",
       .default_address = ".,.",
       .accept_zero = false,
       .pre_text_mode = nullptr,
@@ -407,7 +407,7 @@ void Function::register_posix(BEd &ctx) {
       .address_kind = Function::AddressKind::Range,
       .argument_kind = Function::ArgumentKind::None,
       .input_mode = Function::InputMode::None,
-      .desc = "Print range with line numbers",
+      .desc = "Print a range with line numbers",
       .default_address = ".,.",
       .accept_zero = false,
       .pre_text_mode = nullptr,
@@ -430,7 +430,7 @@ void Function::register_posix(BEd &ctx) {
       .address_kind = Function::AddressKind::Range,
       .argument_kind = Function::ArgumentKind::None,
       .input_mode = Function::InputMode::None,
-      .desc = "Print range",
+      .desc = "Print a range",
       .default_address = ".,.",
       .accept_zero = false,
       .pre_text_mode = nullptr,
@@ -453,7 +453,7 @@ void Function::register_posix(BEd &ctx) {
       .address_kind = Function::AddressKind::None,
       .argument_kind = Function::ArgumentKind::Any,
       .input_mode = Function::InputMode::None,
-      .desc = "Toggle/set prompt.",
+      .desc = "Toggle/set prompt string",
       .default_address = "",
       .accept_zero = false,
       .pre_text_mode = nullptr,
@@ -482,7 +482,7 @@ void Function::register_posix(BEd &ctx) {
       .address_kind = Function::AddressKind::None,
       .argument_kind = Function::ArgumentKind::None,
       .input_mode = Function::InputMode::None,
-      .desc = "Try quitting.",
+      .desc = "Quit, warn once if unsaved changes exist",
       .default_address = "",
       .accept_zero = false,
       .pre_text_mode = nullptr,
@@ -513,7 +513,7 @@ void Function::register_posix(BEd &ctx) {
       .address_kind = Function::AddressKind::None,
       .argument_kind = Function::ArgumentKind::None,
       .input_mode = Function::InputMode::None,
-      .desc = "Force quit.",
+      .desc = "Quit without saving, discarding unsaved changes",
       .default_address = "",
       .accept_zero = false,
       .pre_text_mode = nullptr,
@@ -534,7 +534,7 @@ void Function::register_posix(BEd &ctx) {
       .address_kind = Function::AddressKind::Line,
       .argument_kind = Function::ArgumentKind::File,
       .input_mode = Function::InputMode::None,
-      .desc = "Read from file into buffer.",
+      .desc = "Read a file's contents into the buffer after the given address",
       .default_address = "$",
       .accept_zero = true,
       .pre_text_mode = nullptr,
@@ -581,7 +581,7 @@ void Function::register_posix(BEd &ctx) {
       .address_kind = Function::AddressKind::Range,
       .argument_kind = Function::ArgumentKind::Regex,
       .input_mode = Function::InputMode::None,
-      .desc = "Substitute regex.",
+      .desc = "Substitute pattern in range for replacement",
       .default_address = ".,.",
       .accept_zero = false,
       .pre_text_mode = nullptr,
@@ -620,7 +620,7 @@ void Function::register_posix(BEd &ctx) {
       .address_kind = Function::AddressKind::Range,
       .argument_kind = Function::ArgumentKind::Line,
       .input_mode = Function::InputMode::None,
-      .desc = "Copy a range of lines.",
+      .desc = "Copy a range of lines",
       .default_address = ".,.",
       .accept_zero = false,
       .pre_text_mode = nullptr,
@@ -650,7 +650,7 @@ void Function::register_posix(BEd &ctx) {
       .address_kind = Function::AddressKind::None,
       .argument_kind = Function::ArgumentKind::None,
       .input_mode = Function::InputMode::None,
-      .desc = "Undo last modification to buffer.",
+      .desc = "Undo the last modification to the buffer",
       .default_address = "",
       .accept_zero = false,
       .pre_text_mode = nullptr,
@@ -677,7 +677,7 @@ void Function::register_posix(BEd &ctx) {
       .address_kind = Function::AddressKind::Range,
       .argument_kind = Function::ArgumentKind::File,
       .input_mode = Function::InputMode::None,
-      .desc = "Write buffer to disk.",
+      .desc = "Write a range of lines to disk",
       .default_address = "0,$",
       .accept_zero = true,
       .pre_text_mode = nullptr,
@@ -729,7 +729,7 @@ void Function::register_posix(BEd &ctx) {
       .address_kind = Function::AddressKind::Range,
       .argument_kind = Function::ArgumentKind::None,
       .input_mode = Function::InputMode::None,
-      .desc = "Print line numbers",
+      .desc = "Print the line number of the given address",
       .default_address = "$",
       .accept_zero = true,
       .pre_text_mode = nullptr,
@@ -758,7 +758,7 @@ void Function::register_posix(BEd &ctx) {
       .address_kind = Function::AddressKind::None,
       .argument_kind = Function::ArgumentKind::Shell,
       .input_mode = Function::InputMode::None,
-      .desc = "Run a shell command.",
+      .desc = "Run a shell command",
       .default_address = "",
       .accept_zero = false,
       .pre_text_mode = nullptr,
@@ -785,7 +785,7 @@ void Function::register_posix(BEd &ctx) {
     .address_kind = Function::AddressKind::Line,
     .argument_kind = Function::ArgumentKind::None,
     .input_mode = Function::InputMode::None,
-    .desc = "Prints a line and jumps to it.",
+    .desc = "Print given line and move the cursor to it",
     .default_address = ".+1",
     .accept_zero = true,
     .pre_text_mode = nullptr,
@@ -800,13 +800,16 @@ void Function::register_posix(BEd &ctx) {
       if (addr.number != 0)
         ctx.buffer(addr.buffername).print(ctx, addr.number, addr.number);
       ctx.current() = addr;
+      ctx.prev().buffername = addr.buffername;
+      ctx.prev().start = addr.number;
+      ctx.prev().end = addr.number;
     }
   };
   ctx.eof_op = Function{
     .address_kind = Function::AddressKind::None,
     .argument_kind = Function::ArgumentKind::None,
     .input_mode = Function::InputMode::None,
-    .desc = "Try quitting.",
+    .desc = "Quit, warn once if unsaved changes exist",
     .default_address = "",
     .accept_zero = false,
     .pre_text_mode = nullptr,