diff --git a/README.md b/README.md
index 9b371758..d6b449c4 100644
--- a/README.md
+++ b/README.md
@@ -128,24 +128,16 @@ easy to fork and contribute any changes back upstream.
     $ exec $SHELL -l
     ~~~
 
-5. Install Ruby versions into `~/.rbenv/versions`. For example, to
-   manually compile Ruby [from source](https://github.com/ruby/ruby),
-   download it and run:
-
-    ~~~ sh
-    $ [ -f ./configure ] || autoconf
-    $ ./configure --prefix=$HOME/.rbenv/versions/1.9.3-p327
-    $ make
-    $ make install
-    ~~~
-
-    The [ruby-build][] project, however, provides an `rbenv install`
-    command that simplifies the process of installing new Ruby versions:
+5. Install [ruby-build][], which provides an `rbenv install`
+   command that simplifies the process of installing new Ruby versions.
 
     ~~~
     $ rbenv install 1.9.3-p327
     ~~~
 
+   As an alternative, you can download and compile Ruby yourself into
+   `~/.rbenv/versions/`.
+
 6. Rebuild the shim binaries. You should do this any time you install
    a new Ruby binary (for example, when installing a new Ruby version,
    or when installing a gem that provides a binary).
diff --git a/completions/rbenv.bash b/completions/rbenv.bash
index e3276016..fe0784ac 100644
--- a/completions/rbenv.bash
+++ b/completions/rbenv.bash
@@ -5,8 +5,10 @@ _rbenv() {
   if [ "$COMP_CWORD" -eq 1 ]; then
     COMPREPLY=( $(compgen -W "$(rbenv commands)" -- "$word") )
   else
-    local command="${COMP_WORDS[1]}"
-    local completions="$(rbenv completions "$command")"
+    local words=("${COMP_WORDS[@]}")
+    unset words[0]
+    unset words[$COMP_CWORD]
+    local completions=$(rbenv completions "${words[@]}")
     COMPREPLY=( $(compgen -W "$completions" -- "$word") )
   fi
 }
diff --git a/completions/rbenv.zsh b/completions/rbenv.zsh
index 4739ac10..c439c5aa 100644
--- a/completions/rbenv.zsh
+++ b/completions/rbenv.zsh
@@ -5,14 +5,13 @@ fi
 compctl -K _rbenv rbenv
 
 _rbenv() {
-  local word words completions
+  local words completions
   read -cA words
-  word="${words[2]}"
 
   if [ "${#words}" -eq 2 ]; then
     completions="$(rbenv commands)"
   else
-    completions="$(rbenv completions "${word}")"
+    completions="$(rbenv completions ${words[2,-1]})"
   fi
 
   reply=("${(ps:\n:)completions}")
diff --git a/libexec/rbenv b/libexec/rbenv
index d368d459..76928647 100755
--- a/libexec/rbenv
+++ b/libexec/rbenv
@@ -60,7 +60,7 @@ shopt -u nullglob
 command="$1"
 case "$command" in
 "" | "-h" | "--help" )
-  echo -e "rbenv $(rbenv---version)\n$(rbenv-help)" >&2
+  echo -e "$(rbenv---version)\n$(rbenv-help)" >&2
   ;;
 "-v" )
   exec rbenv---version
diff --git a/libexec/rbenv---version b/libexec/rbenv---version
index fcf94d69..aa9b829d 100755
--- a/libexec/rbenv---version
+++ b/libexec/rbenv---version
@@ -2,9 +2,10 @@
 set -e
 [ -n "$RBENV_DEBUG" ] && set -x
 
-version=v0.3.0
+version=0.3.0
 
 cd "$RBENV_ROOT"
 git_revision="$(git describe --tags HEAD 2>/dev/null || true)"
+git_revision="${git_revision#v}"
 
-echo ${git_revision:-$version}
+echo "rbenv ${git_revision:-$version}"
diff --git a/libexec/rbenv-exec b/libexec/rbenv-exec
index 92ecb72b..5c1aacd8 100755
--- a/libexec/rbenv-exec
+++ b/libexec/rbenv-exec
@@ -7,7 +7,9 @@ if [ "$1" = "--complete" ]; then
   exec rbenv shims --short
 fi
 
+export RBENV_VERSION="$(rbenv-version-name)"
 RBENV_COMMAND="$1"
+
 if [ -z "$RBENV_COMMAND" ]; then
   echo "usage: rbenv exec COMMAND [arg1 arg2...]" >&2
   exit 1
@@ -21,5 +23,7 @@ for script in $(rbenv-hooks exec); do
 done
 
 shift 1
-export PATH="${RBENV_BIN_PATH}:${PATH}"
+if [ "$RBENV_VERSION" != "system" ]; then
+  export PATH="${RBENV_BIN_PATH}:${PATH}"
+fi
 exec -a "$RBENV_COMMAND" "$RBENV_COMMAND_PATH" "$@"
diff --git a/libexec/rbenv-init b/libexec/rbenv-init
index 95b6c403..16916cd5 100755
--- a/libexec/rbenv-init
+++ b/libexec/rbenv-init
@@ -86,7 +86,8 @@ commands=(`rbenv-commands --sh`)
 IFS="|"
 cat <<EOS
 rbenv() {
-  local command="\$1"
+  typeset command
+  command="\$1"
   if [ "\$#" -gt 0 ]; then
     shift
   fi
diff --git a/libexec/rbenv-rehash b/libexec/rbenv-rehash
index 13bd7938..916323a3 100755
--- a/libexec/rbenv-rehash
+++ b/libexec/rbenv-rehash
@@ -39,12 +39,41 @@ create_prototype_shim() {
   cat > "$PROTOTYPE_SHIM_PATH" <<SH
 #!/usr/bin/env bash
 set -e
+[ -n "\$RBENV_DEBUG" ] && set -x
+
+program="\${0##*/}"
+if [ "\$program" = "ruby" ]; then
+  for arg; do
+    case "\$arg" in
+    -e* | -- ) break ;;
+    */* )
+      if [ -f "\$arg" ]; then
+        export RBENV_DIR="\${arg%/*}"
+        break
+      fi
+      ;;
+    esac
+  done
+fi
+
 export RBENV_ROOT="$RBENV_ROOT"
-exec rbenv exec "\${0##*/}" "\$@"
+exec rbenv exec "\$program" "\$@"
 SH
   chmod +x "$PROTOTYPE_SHIM_PATH"
 }
 
+# If the contents of the prototype shim file differ from the contents
+# of the first shim in the shims directory, assume rbenv has been
+# upgraded and the existing shims need to be removed.
+remove_outdated_shims() {
+  for shim in *; do
+    if ! diff "$PROTOTYPE_SHIM_PATH" "$shim" >/dev/null 2>&1; then
+      for shim in *; do rm -f "$shim"; done
+    fi
+    break
+  done
+}
+
 # The basename of each argument passed to `make_shims` will be
 # registered for installation as a shim. In this way, plugins may call
 # `make_shims` with a glob to register many shims at once.
@@ -57,58 +86,27 @@ make_shims() {
   done
 }
 
-# Create an empty array for the list of registered shims.
+# Create an empty array for the list of registered shims and an empty
+# string to use as a search index.
 registered_shims=()
+registered_shims_index=""
 
 # We will keep track of shims registered for installation with the
-# global `reigstered_shims` array and with a global variable for each
-# shim. The array will let us iterate over all registered shims. The
-# global variables will let us quickly check whether a shim with the
-# given name has been registered or not.
+# global `reigstered_shims` array and with a global search index
+# string. The array will let us iterate over all registered shims. The
+# index string will let us quickly check whether a shim with the given
+# name has been registered or not.
 register_shim() {
   local shim="$@"
-  local var="$(shim_variable_name "$shim")"
-
-  if [ -z "${!var}" ]; then
-    registered_shims[${#registered_shims[*]}]="$shim"
-    eval "${var}=1"
-  fi
-}
-
-# To compute the global variable name for a given shim we must first
-# escape any non-alphanumeric characters. If the shim name is
-# alphanumeric (including a hyphen or underscore) we can take a
-# shorter path. Otherwise, we must iterate over each character and
-# escape the non-alphanumeric ones using `printf`.
-shim_variable_name() {
-  local shim="$1"
-  local result="_shim_"
-
-  if [[ ! "$shim" =~ [^[:alnum:]_-] ]]; then
-    shim="${shim//_/_5f}"
-    shim="${shim//-/_2d}"
-    result="$result$shim"
-  else
-    local length="${#shim}"
-    local char i
-
-    for ((i=0; i<length; i++)); do
-      char="${shim:$i:1}"
-      if [[ "$char" =~ [[:alnum:]] ]]; then
-        result="$result$char"
-      else
-        result="$result$(printf "_%02x" \'"$char")"
-      fi
-    done
-  fi
-
-  echo "$result"
+  registered_shims["${#registered_shims[@]}"]="$shim"
+  registered_shims_index="$registered_shims_index/$shim/"
 }
 
 # To install all the registered shims, we iterate over the
 # `registered_shims` array and create a link if one does not already
 # exist.
 install_registered_shims() {
+  local shim
   for shim in "${registered_shims[@]}"; do
     [ -e "$shim" ] || ln -f "$PROTOTYPE_SHIM_PATH" "$shim"
   done
@@ -119,11 +117,10 @@ install_registered_shims() {
 # in the directory but has not been registered as a shim should be
 # removed.
 remove_stale_shims() {
-  local var
+  local shim
   for shim in *; do
-    var="$(shim_variable_name "$shim")"
-    if [ -z "${!var}" ]; then
-      rm -f "$shim" 
+    if [[ "$registered_shims_index" != *"/$shim/"* ]]; then
+      rm -f "$shim"
     fi
   done
 }
@@ -131,10 +128,11 @@ remove_stale_shims() {
 
 # Change to the shims directory.
 cd "$SHIM_PATH"
+shopt -s nullglob
 
 # Create the prototype shim, then register shims for all known binaries.
 create_prototype_shim
-shopt -s nullglob
+remove_outdated_shims
 make_shims ../versions/*/bin/*
 
 # Restore the previous working directory.
diff --git a/libexec/rbenv-sh-rehash b/libexec/rbenv-sh-rehash
new file mode 100755
index 00000000..9cc75265
--- /dev/null
+++ b/libexec/rbenv-sh-rehash
@@ -0,0 +1,13 @@
+#!/usr/bin/env bash
+set -e
+[ -n "$RBENV_DEBUG" ] && set -x
+
+# Provide rbenv completions
+if [ "$1" = "--complete" ]; then
+  exec rbenv-rehash --complete
+fi
+
+# When rbenv shell integration is enabled, delegate to rbenv-rehash,
+# then tell the shell to empty its command lookup cache.
+rbenv-rehash
+echo "hash -r"
diff --git a/libexec/rbenv-version-file b/libexec/rbenv-version-file
index 9b678769..e9451f42 100755
--- a/libexec/rbenv-version-file
+++ b/libexec/rbenv-version-file
@@ -2,14 +2,19 @@
 set -e
 [ -n "$RBENV_DEBUG" ] && set -x
 
-root="$RBENV_DIR"
-while [ -n "$root" ]; do
-  if [ -e "${root}/.rbenv-version" ]; then
-    echo "${root}/.rbenv-version"
-    exit
-  fi
-  root="${root%/*}"
-done
+find_local_version_file() {
+  local root="$1"
+  while [ -n "$root" ]; do
+    if [ -e "${root}/.rbenv-version" ]; then
+      echo "${root}/.rbenv-version"
+      exit
+    fi
+    root="${root%/*}"
+  done
+}
+
+find_local_version_file "$RBENV_DIR"
+[ "$RBENV_DIR" = "$PWD" ] || find_local_version_file "$PWD"
 
 global_version_file="${RBENV_ROOT}/version"