diff --git a/download-and-install b/download-and-install
index 5e14867..1ae48f3 100755
--- a/download-and-install
+++ b/download-and-install
@@ -144,13 +144,13 @@ if [[ -z $smartcd_previously_installed ]]; then
     echo
     echo "To get started, create a few scripts.  Its easy!  Try this:"
     echo
-    echo "    echo 'echo hello there from \$(pwd)' | smartcd edit enter"
-    echo "    echo 'echo goodbye from \$(pwd)' | smartcd edit leave"
+    echo "    echo 'echo hello there from \$PWD' | smartcd edit enter"
+    echo "    echo 'echo goodbye from \$PWD' | smartcd edit leave"
     echo
     echo "Then simply leave the directory and come back.  For a more practical"
     echo "example, how about tweaking your PATH?"
     echo
-    echo "    echo \"autostash PATH=\$(pwd)/bin:\\\$PATH\" | smartcd edit enter"
+    echo "    echo \"autostash PATH=\$PWD/bin:\\\$PATH\" | smartcd edit enter"
     echo
     echo "(side note: the quoting rules when editing in this fashion can be a bit"
     echo "awkward, so feel free to run \`smartcd edit\` interactively too!"
diff --git a/lib/core/arrays b/lib/core/arrays
index 28c5209..3ed6a01 100644
--- a/lib/core/arrays
+++ b/lib/core/arrays
@@ -139,7 +139,7 @@ function ashift() {
     fi
 }
 
-# Bash requires the array be quoted, zsh requires it not
+# Bash requires the array to be quoted, zsh does not.
 function aunshift() {
     local var=$1; shift
 
diff --git a/lib/core/completion b/lib/core/completion
index b53073e..b545f53 100644
--- a/lib/core/completion
+++ b/lib/core/completion
@@ -6,9 +6,15 @@
 #
 
 if [[ -n $ZSH_VERSION ]]; then
-    autoload -U compinit
-    compinit
-    autoload -U +X bashcompinit && bashcompinit
+    # Only load/call compinit once.
+    if [[ -z $_comp_dumpfile ]]; then
+        autoload -U compinit
+        compinit
+    fi
+    # Only load/call bashcompinit once.
+    if [[ -z $functions[complete] ]]; then
+        autoload -U +X bashcompinit && bashcompinit
+    fi
 fi
 
 function _smartcd_completion() {
diff --git a/lib/core/smartcd b/lib/core/smartcd
index 4003057..a24ef08 100644
--- a/lib/core/smartcd
+++ b/lib/core/smartcd
@@ -1,4 +1,5 @@
 ################################################################################
+
 # smartcd - cd with some oomph
 #
 #   Copyright (c) 2009,2012 Dave Olszewski <cxreg@pobox.com>
@@ -184,7 +185,7 @@ function smartcd() {
     case $command in
         -h|help|'') echo $usage;;
      cd|pushd|popd) shift; _smartcd $command "$@"; return $?;;
-           reenter) local dir="$(pwd)"
+           reenter) local dir="$PWD"
                     _smartcd cd ..
                     _smartcd cd "$dir"
                     ;;
@@ -203,7 +204,7 @@ function smartcd() {
                             --global) whence="global";;
                             --system) system="true";;
                                --all) whence="all"; system="both";;
-                                   *) echo "$opt unknown"
+                                   *) echo "$opt unknown. Available: [--host|--global|--all] [--system]."
                                       return
                                       ;;
                         esac
@@ -211,7 +212,6 @@ function smartcd() {
                     done
 
                     local type=$1
-                    shift
                     case $type in
                                    enter|leave) ;;
                          bash_enter|bash_leave) type="${type#bash_}";;
@@ -219,16 +219,19 @@ function smartcd() {
                                                 return
                                                 ;;
                     esac
+                    shift
                     [[ -n $type ]] && _smartcd_file_check "$type" "$whence" "$system" "$command" "$@"
                     ;;
           template) shift; smartcd_template "$@";;
-             setup) shift; local setup=$1; shift;
+             setup) shift; local setup=$1
                     case $setup in
                              cd|pushd|popd) setup_smartcd_function $setup;;
                         prompt-hook|prompt) setup_smartcd_prompt_hook;;
                           chpwd-hook|chpwd) setup_smartcd_chpwd_hook;;
                             exit-hook|exit) setup_smartcd_exit_hook;;
                                 completion) _smartcd_load "completion";;
+                                         *) echo "Usage: smartcd $command (cd|pushd|popd|prompt[-hook]|chpwd[-hook]|exit[-hook]|completion)"
+                                            return ;;
                     esac
                     ;;
           on-leave) local code=${2//\\/\\\\};
@@ -449,7 +452,7 @@ function _smartcd() {
     IFS="$_old_ifs"
 
     if (( $rv != 0 )); then return $rv; fi
-    local whereto="$(pwd)"
+    local whereto="$PWD"
     _smartcd_last_run_for="x$whereto"
 
     # If zsh, turn autopushd off temporarily to avoid extra pushes
@@ -497,18 +500,24 @@ function _smartcd() {
         apop leave_stack >/dev/null
     done
 
-    local host=${SMARTCD_HOSTNAME:-$(hostname)}
+    local host=${SMARTCD_HOSTNAME:-${HOST:-$(hostname)}}
 
     # Run leave_stack in lowest to highest
     local stack_size=$(alen leave_stack)
     : ${stack_size:=0}
     local smartcd_runmode=leave
+
+    # Set vars used in while loops.
+    if [[ $stack_size -gt 0 ]]; then
+        local sysdir=$(_smartcd_sysdir)
+    fi
+
     while (( $stack_size >= 1 )); do
         # ashift in a sub-shell doesn't work
         local smartcd_current_dir="$(afirst leave_stack)"
         ashift leave_stack >/dev/null
 
-        # Set this just in case we are not able to actualy chdir to $smartcd_current_dir
+        # Set this in case we are not able to actually chdir to $smartcd_current_dir.
         local varstash_dir="$smartcd_current_dir"
 
         if [[ -d "$smartcd_current_dir" ]]; then
@@ -528,7 +537,6 @@ function _smartcd() {
         # can check things out
 
         # 1) Run system-wide global leave script
-        local sysdir=$(_smartcd_sysdir)
         local confdir="$sysdir/scripts$smartcd_current_dir"
         if [[ -f "$confdir/bash_leave" ]]; then
             if (( ${SMARTCD_QUIET:-0} == 0 )); then
@@ -663,7 +671,6 @@ function _smartcd() {
         done
 
         # 1) Run system-wide global enter script
-        local sysdir=$(_smartcd_sysdir)
         local confdir="$sysdir/scripts$smartcd_current_dir"
         if [[ -f "$confdir/bash_enter" ]]; then
             if (( ${SMARTCD_QUIET:-0} == 0 )); then
@@ -757,7 +764,7 @@ function _smartcd() {
 }
 
 function _smartcd_hook() {
-    local cwd="$(pwd)"
+    local cwd="$PWD"
 
     # Skip this if we already ran smartcd for this directory
     if [[ "x$cwd" != "$_smartcd_last_run_for" ]]; then
@@ -815,6 +822,9 @@ function setup_smartcd_chpwd_hook() {
             return
         fi
         apush chpwd_functions _smartcd_hook
+    else
+        echo "chpwd hook is not supported for your shell."
+        return
     fi
 }
 
@@ -866,13 +876,13 @@ function _smartcd_file() {
     if [[ -n $ZSH_VERSION ]]; then
         setopt localoptions && setopt ksharrays
         local this_file=${funcsourcetrace[0]}
-        this_file="${this_file%:*}"
+        # Remove line number and use absolute path.
+        this_file="${${this_file%:*}:a}"
     else
         local this_file="$BASH_SOURCE"
     fi
-    if [[ "${this_file%/.smartcd/lib/core/smartcd}" == $HOME ]]; then
-        this_file=${this_file/#$HOME/\~}
-    fi
+    # Replace $HOME with ~ at the beginning.
+    this_file=${this_file/#$HOME/\~}
     echo "$this_file"
 }
 
diff --git a/lib/core/smartcd_edit b/lib/core/smartcd_edit
index f960766..d854017 100644
--- a/lib/core/smartcd_edit
+++ b/lib/core/smartcd_edit
@@ -1,7 +1,7 @@
 # wrapper function to preserve legacy usage
 function smartcd_edit() {
     local type="$1"
-    local dir="${2:-$(pwd)}"
+    local dir="${2:-$PWD}"
 
     case $type in
         bash_enter|bash_leave) local file=$type; type="${type#bash_}";;
@@ -169,7 +169,7 @@ function _smartcd_file_check() {
             return
         fi
     else
-        dir="$(pwd)"
+        dir="$PWD"
     fi
 
     if [[ -n $system ]]; then
@@ -178,7 +178,7 @@ function _smartcd_file_check() {
         local base=$(_smartcd_base)
     fi
     if [[ $whence = "host" ]]; then
-        local host=${SMARTCD_HOSTNAME:-$(hostname)}
+        local host=${SMARTCD_HOSTNAME:-${HOST:-$(hostname)}}
         base="$base/hosts/$host"
     fi
     local file="bash_$type"
diff --git a/lib/core/smartcd_template b/lib/core/smartcd_template
index 38c7874..a323832 100644
--- a/lib/core/smartcd_template
+++ b/lib/core/smartcd_template
@@ -68,7 +68,7 @@ EOF
                         if [[ -f "$base/templates/$name" ]]; then
                             echo "Template $name already exists, run \"smartcd template edit $name\" to modify it"
                         else
-                            smartcd_template _init "$name" "$(pwd)"
+                            smartcd_template _init "$name" "$PWD"
                             smartcd_template edit "$name"
                         fi
                     else
@@ -137,7 +137,7 @@ EOF
                     local name="$1"
                     if [[ -n $name ]]; then
                         if [[ -f "$base/templates/$name" ]]; then
-                            local current_dir=$(pwd)
+                            local current_dir=$PWD
 
                             local mode= line=
                             while builtin read -r line; do
@@ -201,7 +201,7 @@ EOF
                                 esac
                             done < "$base/templates/$name"
                             IFS="$_old_ifs"
-                            _smartcd_exec "$contents" "$(pwd)"
+                            _smartcd_exec "$contents" "$PWD"
                         else
                             echo "Template $name not found"
                         fi
diff --git a/lib/core/varstash b/lib/core/varstash
index 2ad4afa..a12d6fc 100644
--- a/lib/core/varstash
+++ b/lib/core/varstash
@@ -71,7 +71,7 @@ function stash() {
     fi
 
     if [[ -n $1 ]] && [[ -z $run_from_smartcd ]] && [[ -z $run_from_autostash ]]; then
-        local working_dir="${varstash_dir:-$(pwd)}"
+        local working_dir="${varstash_dir:-$PWD}"
         local smartcd_dir="$(_smartcd_base)/scripts$working_dir"
         local help_action="stashing a variable"
         local help_dir=$smartcd_dir
@@ -211,7 +211,7 @@ function stash() {
 
 function autostash() {
     if [[ -n $1 ]] && [[ -z $run_from_smartcd ]]; then
-        local working_dir="${varstash_dir:-$(pwd)}"
+        local working_dir="${varstash_dir:-$PWD}"
         local smartcd_dir="$(_smartcd_base)/scripts$working_dir"
         local help_action="autostashing a variable"
         local help_dir=$smartcd_dir
@@ -241,7 +241,7 @@ function autostash() {
 
 function unstash() {
     if [[ -n $1 ]] && [[ -z $run_from_smartcd ]] && [[ -z $run_from_autounstash ]]; then
-        local working_dir=${varstash_dir:-$(pwd)}
+        local working_dir=${varstash_dir:-$PWD}
         local smartcd_dir="$(_smartcd_base)/scripts$working_dir"
         local help_action="unstashing a variable"
         local help_dir=$smartcd_dir
diff --git a/t/smartcd.t b/t/smartcd.t
index 1496af4..08872ab 100644
--- a/t/smartcd.t
+++ b/t/smartcd.t
@@ -1,7 +1,7 @@
 # Set up smartcd
 mkdir -p tmphome
 oldhome=$HOME
-export HOME="$(pwd)/tmphome"
+export HOME="$PWD/tmphome"
 
 
 # Load testing library
@@ -48,17 +48,17 @@ like "${output-_}" "this is a leaving test" "bash_leave executed successfully us
 echo | smartcd edit enter "$dir"
 echo | smartcd edit leave "$dir"
 
-linkdest="$(pwd)/$dir/destination"
+linkdest="$PWD/$dir/destination"
 link="$dir/symlink"
 mkdir -p "$linkdest"
 ln -s destination "$link"
 smartcd cd -P $link
-is "_$(pwd)" "_$linkdest" "cd -P still works"
+is "_$PWD" "_$linkdest" "cd -P still works"
 smartcd cd ../..
 
 spacedir="dir with a space"
 mkdir -p "$spacedir"
-smartcd_spacedir="$HOME/.smartcd/scripts$(pwd)/$spacedir"
+smartcd_spacedir="$HOME/.smartcd/scripts$PWD/$spacedir"
 mkdir -p "$smartcd_spacedir"
 echo 'echo -n "1 "' > "$smartcd_spacedir/bash_enter"
 echo 'echo 2' > "$smartcd_spacedir/bash_leave"
@@ -68,7 +68,7 @@ is "${output-_}" "1 2" "could enter and leave a directory with a space"
 echo 'echo 4' > "$smartcd_spacedir/bash_leave"
 spacedir2="dir with a space/subdir"
 mkdir -p "$spacedir2"
-smartcd_spacedir2="$HOME/.smartcd/scripts$(pwd)/$spacedir2"
+smartcd_spacedir2="$HOME/.smartcd/scripts$PWD/$spacedir2"
 mkdir -p "$smartcd_spacedir2"
 echo 'echo -n "2 "' > "$smartcd_spacedir2/bash_enter"
 echo 'echo -n "3 "' > "$smartcd_spacedir2/bash_leave"
diff --git a/t/varstash.t b/t/varstash.t
index 284e227..4ca42d3 100644
--- a/t/varstash.t
+++ b/t/varstash.t
@@ -109,12 +109,12 @@ is "_$(alast thing)" "_three four" "unstashed array"
 oldhome=$HOME
 stash HOME
 mkdir -p tmphome
-export HOME=$(pwd)/tmphome
+export HOME=$PWD/tmphome
 
 VARSTASH_AUTOCONFIG=1
 oldshell=$SHELL
 autostash SHELL
-config_file="$HOME/.smartcd/scripts$(pwd)/bash_enter"
+config_file="$HOME/.smartcd/scripts$PWD/bash_enter"
 config_file_exists=$([[ -f $config_file ]] && echo "yes")
 
 like "${config_file_exists-_}" "yes" "created smartcd file"