diff --git a/README.md b/README.md
index 954ee8a5..40d67f1e 100644
--- a/README.md
+++ b/README.md
@@ -170,15 +170,19 @@ The special version name `system` tells pyenv to use the system Python
 When run without a version number, `pyenv global` reports the
 currently configured global version.
 
-_pyenv extension_
-
-You can specify multiple versions for global Python. Commands within
-these versions are searched by specified order.
+And also, you can specify multiple versions as global Python. Commands
+within these Python versions are searched by specified order.
 
     $ pyenv global 2.7.3 3.2.3
     $ pyenv global
     2.7.3
     3.2.3
+    $ pyenv which python2.7
+    /home/yyuu/.pyenv/versions/2.7.3/bin/python2.7
+    $ pyenv which python3.2
+    /home/yyuu/.pyenv/versions/3.2.3/bin/python3.2
+    $ pyenv which python
+    /home/yyuu/.pyenv/versions/2.7.3/bin/python
 
 ### <a name="section_3.2"></a> 3.2 pyenv local
 
@@ -195,9 +199,19 @@ configured local version. You can also unset the local version:
 
     $ pyenv local --unset
 
-_pyenv extension_
+And also, you can specify multiple versions as local Python. Commands
+within these Python versions are searched by specified order.
 
-You can specify multiple versions for local Python.
+    $ pyenv local 2.7.3 3.2.3
+    $ pyenv local
+    2.7.3
+    3.2.3
+    $ pyenv which python2.7
+    /home/yyuu/.pyenv/versions/2.7.3/bin/python2.7
+    $ pyenv which python3.2
+    /home/yyuu/.pyenv/versions/3.2.3/bin/python3.2
+    $ pyenv which python
+    /home/yyuu/.pyenv/versions/2.7.3/bin/python
 
 ### <a name="section_3.3"></a> 3.3 pyenv shell
 
@@ -219,6 +233,16 @@ prefer not to use shell integration, you may simply set the
 
     $ export PYENV_VERSION=pypy-1.9
 
+And also, you can specify multiple versions via `PYENV_VERSION`
+environment variable in your shell.
+
+    $ pyenv shell pypy-1.9 2.7.3
+    $ echo $PYENV_VERSION
+    pypy-1.9:2.7.3
+    $ pyenv version
+    pypy-1.9 (set by PYENV_VERSION environment variable)
+    2.7.3 (set by PYENV_VERSION environment variable)
+
 ### <a name="section_3.4"></a> 3.4 pyenv versions
 
 Lists all Python versions known to pyenv, and shows an asterisk next to
diff --git a/libexec/pyenv-global b/libexec/pyenv-global
index 70af07b2..f3dc712b 100755
--- a/libexec/pyenv-global
+++ b/libexec/pyenv-global
@@ -8,19 +8,19 @@ if [ "$1" = "--complete" ]; then
   exec pyenv-versions --bare
 fi
 
-PYENV_VERSION=($@)
+versions=($@)
 PYENV_VERSION_FILE="${PYENV_ROOT}/version"
 
-if [ -n "$PYENV_VERSION" ]; then
-  pyenv-version-file-write "$PYENV_VERSION_FILE" "${PYENV_VERSION[@]}"
+if [ -n "$versions" ]; then
+  pyenv-version-file-write "$PYENV_VERSION_FILE" "${versions[@]}"
 else
-  IFS=: PYENV_VERSION=($(
+  IFS=: versions=($(
     pyenv-version-file-read "$PYENV_VERSION_FILE" ||
     pyenv-version-file-read "${PYENV_ROOT}/global" ||
     pyenv-version-file-read "${PYENV_ROOT}/default" ||
     echo system
   ))
-  for version in "${PYENV_VERSION[@]}"; do
+  for version in "${versions[@]}"; do
     echo "$version"
   done
 fi
diff --git a/libexec/pyenv-local b/libexec/pyenv-local
index 8f41feab..c7c72d35 100755
--- a/libexec/pyenv-local
+++ b/libexec/pyenv-local
@@ -9,21 +9,21 @@ if [ "$1" = "--complete" ]; then
   exec pyenv-versions --bare
 fi
 
-PYENV_VERSION=($@)
+versions=($@)
 PYENV_VERSION_FILE=".pyenv-version"
 
-if [ "$PYENV_VERSION" = "--unset" ]; then
+if [ "$versions" = "--unset" ]; then
   rm -f "$PYENV_VERSION_FILE"
-elif [ -n "$PYENV_VERSION" ]; then
-  pyenv-version-file-write "$PYENV_VERSION_FILE" "${PYENV_VERSION[@]}"
+elif [ -n "$versions" ]; then
+  pyenv-version-file-write "$PYENV_VERSION_FILE" "${versions[@]}"
 else
-  IFS=: PYENV_VERSION=($(
+  IFS=: versions=($(
     pyenv-version-file-read "$PYENV_VERSION_FILE" ||
     { echo "pyenv: no local version configured for this directory"
       exit 1
     } >&2
   ))
-  for version in "${PYENV_VERSION[@]}"; do
+  for version in "${versions[@]}"; do
     echo "$version"
   done
 fi
diff --git a/libexec/pyenv-prefix b/libexec/pyenv-prefix
index c1569f7b..1869983e 100755
--- a/libexec/pyenv-prefix
+++ b/libexec/pyenv-prefix
@@ -9,19 +9,21 @@ if [ "$1" = "--complete" ]; then
 fi
 
 if [ -n "$1" ]; then
-  export PYENV_VERSION=($@)
+  versions=($@)
+  IFS=: PYENV_VERSION="${versions[*]}"
+  export PYENV_VERSION
 else
-  IFS=: PYENV_VERSION=($(pyenv-version-name))
+  IFS=: versions=($(pyenv-version-name))
 fi
 
-if [ "$PYENV_VERSION" = "system" ]; then
+if [ "$versions" = "system" ]; then
   PYTHON_PATH="$(pyenv-which python)"
   echo "${PYTHON_PATH%/*}"
   exit
 fi
 
 PYENV_PREFIX_PATHS=()
-for version in "${PYENV_VERSION[@]}"; do
+for version in "${versions[@]}"; do
   PYENV_PREFIX_PATH="${PYENV_ROOT}/versions/${version}"
   if [ -d "$PYENV_PREFIX_PATH" ]; then
     PYENV_PREFIX_PATHS=("${PYENV_PREFIX_PATHS[@]}" "$PYENV_PREFIX_PATH")
diff --git a/libexec/pyenv-sh-shell b/libexec/pyenv-sh-shell
index b1f3fafa..5b47b739 100755
--- a/libexec/pyenv-sh-shell
+++ b/libexec/pyenv-sh-shell
@@ -9,9 +9,9 @@ if [ "$1" = "--complete" ]; then
   exec pyenv-versions --bare
 fi
 
-version="$1"
+versions=("$@")
 
-if [ -z "$version" ]; then
+if [ -z "$versions" ]; then
   if [ -z "$PYENV_VERSION" ]; then
     echo "pyenv: no shell-specific version configured" >&2
     exit 1
@@ -21,12 +21,13 @@ if [ -z "$version" ]; then
   fi
 fi
 
-if [ "$version" = "--unset" ]; then
+if [ "$versions" = "--unset" ]; then
   echo "unset PYENV_VERSION"
   exit 1
 fi
 
 # Make sure the specified version is installed.
-pyenv-prefix $version >/dev/null
+pyenv-prefix "${versions[@]}" >/dev/null
 
-echo "export PYENV_VERSION=\"${version}\""
+IFS=: PYENV_VERSION="${versions[*]}"
+echo "export PYENV_VERSION=\"${PYENV_VERSION}\""
diff --git a/libexec/pyenv-version-file-write b/libexec/pyenv-version-file-write
index 9904c8ef..cca0c36a 100755
--- a/libexec/pyenv-version-file-write
+++ b/libexec/pyenv-version-file-write
@@ -4,23 +4,18 @@ set -e
 
 PYENV_VERSION_FILE="$1"
 shift
-PYENV_VERSION=()
-for version in "$@"; do
-  PYENV_VERSION=("${PYENV_VERSION[@]}" "$version")
-done
+versions=("$@")
 
-if [ -z "$PYENV_VERSION" ] || [ -z "$PYENV_VERSION_FILE" ]; then
+if [ -z "$versions" ] || [ -z "$PYENV_VERSION_FILE" ]; then
   echo "usage: pyenv write-version-file FILENAME VERSIONS..." >&2
   exit 1
 fi
 
 # Make sure the specified version is installed.
-for version in "${PYENV_VERSION[@]}"; do
-  pyenv-prefix "$version" >/dev/null
-done
+pyenv-prefix "${vesions[@]}" >/dev/null
 
 # Write the version out to disk.
 rm -f "$PYENV_VERSION_FILE"
-for version in "${PYENV_VERSION[@]}"; do
+for version in "${versions[@]}"; do
   echo "$version" >> "$PYENV_VERSION_FILE"
 done
diff --git a/libexec/pyenv-version-name b/libexec/pyenv-version-name
index c09f7255..763a2094 100755
--- a/libexec/pyenv-version-name
+++ b/libexec/pyenv-version-name
@@ -2,17 +2,22 @@
 set -e
 [ -n "$PYENV_DEBUG" ] && set -x
 
-if [ -z "$PYENV_VERSION" ]; then
+if [ -n "$PYENV_VERSION" ]; then
+# IFS=: versions=($(${PYENV_VERSION})) # this does not work on zsh without `setopt shwordsplit`.
+  versions=($(echo "${PYENV_VERSION}" | tr ":" " "))
+else
   PYENV_VERSION_FILE="$(pyenv-version-file)"
-  IFS=: PYENV_VERSION=($(pyenv-version-file-read "$PYENV_VERSION_FILE" || true))
+  IFS=: versions=($(pyenv-version-file-read "$PYENV_VERSION_FILE" || true))
+  IFS=: PYENV_VERSION="${versions[*]}"
+  export PYENV_VERSION
 fi
 
-if [ -z "$PYENV_VERSION" ] || [ "$PYENV_VERSION" = "system" ] ; then
+if [ -z "$versions" ] || [ "$versions" = "system" ] ; then
   echo "system"
   exit
 fi
 
-for version in "${PYENV_VERSION[@]}"; do
+for version in "${versions[@]}"; do
   PYENV_VERSION_PATH="${PYENV_ROOT}/versions/${version}"
   
   if [ ! -d "$PYENV_VERSION_PATH" ]; then
@@ -21,4 +26,4 @@ for version in "${PYENV_VERSION[@]}"; do
   fi
 done
 
-IFS=: echo "${PYENV_VERSION[*]}"
+echo "${PYENV_VERSION}"
diff --git a/libexec/pyenv-which b/libexec/pyenv-which
index bf246bc0..030ea6dc 100755
--- a/libexec/pyenv-which
+++ b/libexec/pyenv-which
@@ -41,7 +41,7 @@ remove_from_path() {
 }
 
 IFS=: versions=($(pyenv-version-name))
-PYENV_VERSION=("${versions[@]}")
+IFS=: PYENV_VERSION="${versions[*]}"
 PYENV_COMMAND="$1"
 
 if [ -z "$PYENV_COMMAND" ]; then
@@ -49,7 +49,7 @@ if [ -z "$PYENV_COMMAND" ]; then
   exit 1
 fi
 
-for version in "${PYENV_VERSION[@]}"; do
+for version in "${versions[@]}"; do
   if [ "$version" = "system" ]; then
     PATH="$(remote_from_path "${PYENV_ROOT}/shims")"
     PYENV_COMMAND_PATH="$(command -v "$PYENV_COMMAND")"