diff --git a/bin/tmuxifier b/bin/tmuxifier
index 5539aa5..d3923d3 100755
--- a/bin/tmuxifier
+++ b/bin/tmuxifier
@@ -3,11 +3,12 @@ set -e
 [ -n "$TMUXIFIER_DEBUG" ] && set -x
 
 resolve_link() {
-  $(type -p greadlink readlink | head -1) $1
+  $(type -p greadlink readlink | head -1) "$1"
 }
 
 abs_dirname() {
-  local cwd="$(pwd)"
+  local cwd
+  cwd="$(pwd)"
   local path="$1"
 
   while [ -n "$path" ]; do
@@ -20,48 +21,63 @@ abs_dirname() {
   cd "$cwd"
 }
 
-if [ -z "${TMUXIFIER}" ]; then
-  # Set TMUXIFIER relative to the "tmuxifier" executable.
-  export TMUXIFIER="$(dirname "$(abs_dirname "$0")")"
-else
-  # Strip any trailing slash (/) characters from TMUXIFIER variable.
-  export TMUXIFIER="${TMUXIFIER%/}"
-fi
+main() {
+  if [ -z "${TMUXIFIER}" ]; then
+    # Set TMUXIFIER relative to the "tmuxifier" executable.
+    export TMUXIFIER="$(dirname "$(abs_dirname "$0")")"
+  else
+    # Strip any trailing slash (/) characters from TMUXIFIER variable.
+    export TMUXIFIER="${TMUXIFIER%/}"
+  fi
 
-# Load tmuxifier environment variables.
-source "$TMUXIFIER/lib/env.sh"
+  # Bootstrap tmuxifier.
+  source "$TMUXIFIER/lib/load.sh"
 
-# Add tmuxifier's internal commands to PATH.
-export PATH="$TMUXIFIER/libexec:$PATH"
+  # Check Tmux version.
+  export TMUXIFIER_MIN_TMUX_VERSION="1.6"
+  if [ "$(tmuxifier-tmux-version "$TMUXIFIER_MIN_TMUX_VERSION")" == "<" ]; then
+    echo -e "ERROR: Tmuxifier requires Tmux v${TMUXIFIER_MIN_TMUX_VERSION}" \
+      "or newer. You have v$(tmuxifier-tmux-version)." >&2
+    exit 1
+  fi
 
-# Check Tmux version.
-export TMUXIFIER_MIN_TMUX_VERSION="1.6"
-if [ "$(tmuxifier-tmux-version "$TMUXIFIER_MIN_TMUX_VERSION")" == "<" ]; then
-  echo -e "ERROR: Tmuxifier requires Tmux v${TMUXIFIER_MIN_TMUX_VERSION}" \
-    "or newer. You have v$(tmuxifier-tmux-version)." >&2
-  exit 1
-fi
+  # Get command and shift arguments.
+  local command="$1"
+  shift 1
 
-# Parse given command
-command="$1"
-case "$command" in
-  "" | "-h" | "--help")
-    echo -e "tmuxifier $(tmuxifier-version)\n$(tmuxifier-help)" >&2
-    ;;
+  # Resolve to full command name if an alias is given.
+  command="$(tmuxifier-alias "$command" || echo "$command")"
 
-  "-v" | "--version")
-    tmuxifier-version
-    ;;
+  case "$command" in
+    "" | "-h" | "--help")
+      echo -e "tmuxifier $(tmuxifier-version)\n$(tmuxifier-help)" >&2
+      ;;
 
-  *)
-    ! command_path="$(tmuxifier-resolve-command-path "$command")"
+    "-v" | "--version")
+      tmuxifier-version
+      ;;
 
-    if [ -z "$command_path" ]; then
-      echo "tmuxifier: no such command '$command'" >&2
-      exit 1
-    fi
+    *)
+      local command_path
+      local func_name
 
-    shift 1
-    exec "$command_path" "$@"
-    ;;
-esac
+      func_name="tmuxifier-$command"
+
+      # Check if command is available as a function.
+      if declare -f "$func_name" > /dev/null; then
+        "$func_name" "$@"
+      else
+        # Fall back to libexec executable.
+        command_path="$(tmuxifier-resolve-command-path "$command")" || true
+        if [ -z "$command_path" ]; then
+          echo "tmuxifier: no such command '$command'" >&2
+          exit 1
+        fi
+
+        exec "$command_path" "$@"
+      fi
+      ;;
+  esac
+}
+
+main "$@"
diff --git a/lib/commands/alias.sh b/lib/commands/alias.sh
new file mode 100644
index 0000000..e16a346
--- /dev/null
+++ b/lib/commands/alias.sh
@@ -0,0 +1,56 @@
+# Resolve a tmuxifier command alias to its full command name.
+#
+# Usage:
+#   tmuxifier-alias <alias>
+#
+# Arguments:
+#   $1 - Alias to resolve
+#
+# Output:
+#   The full command name if alias is recognized, empty otherwise.
+#
+# Returns:
+#   0 - Alias was recognized
+#   1 - Alias was not recognized
+tmuxifier-alias() {
+  # Provide tmuxifier help
+  if calling-help "$@"; then
+    echo "usage: tmuxifier alias <alias>
+
+Resolve a command alias to it's full name."
+    return
+  fi
+
+  case "$1" in
+    "session" | "ses" | "s")
+      echo "load-session"
+      ;;
+    "window" | "win" | "w")
+      echo "load-window"
+      ;;
+    "new-ses" | "nses" | "ns")
+      echo "new-session"
+      ;;
+    "new-win" | "nwin" | "nw")
+      echo "new-window"
+      ;;
+    "edit-ses" | "eses" | "es")
+      echo "edit-session"
+      ;;
+    "edit-win" | "ewin" | "ew")
+      echo "edit-window"
+      ;;
+    "l")
+      echo "list"
+      ;;
+    "list-ses" | "lses" | "ls")
+      echo "list-sessions"
+      ;;
+    "list-win" | "lwin" | "lw")
+      echo "list-windows"
+      ;;
+    *)
+      return 1
+      ;;
+  esac
+}
diff --git a/lib/commands/resolve-command-path.sh b/lib/commands/resolve-command-path.sh
new file mode 100644
index 0000000..3712985
--- /dev/null
+++ b/lib/commands/resolve-command-path.sh
@@ -0,0 +1,43 @@
+# Resolve the absolute path to a tmuxifier command or alias.
+#
+# Usage:
+#   tmuxifier-resolve-command-path <command_or_alias>
+#
+# Arguments:
+#   $1 - Command name or alias to resolve
+#
+# Output:
+#   The absolute path to the command executable, or empty if not found.
+#
+# Returns:
+#   0 - Command was found
+#   1 - Command was not found
+tmuxifier-resolve-command-path() {
+  # Provide tmuxifier help
+  if calling-help "$@"; then
+    echo "usage: tmuxifier resolve-command-path <command_or_alias>
+
+Outputs the absolute path to the given command or command alias."
+    return
+  fi
+
+  local command_path=""
+
+  if [ -n "$1" ]; then
+    # Look for executable file, not functions.
+    command_path="$(type -P "tmuxifier-$1" 2> /dev/null)" || true
+    if [ -z "$command_path" ]; then
+      local resolved
+      resolved="$(tmuxifier-alias "$1")"
+      if [ -n "$resolved" ]; then
+        command_path="$(type -P "tmuxifier-$resolved" 2> /dev/null)" || true
+      fi
+    fi
+  fi
+
+  if [ -n "$command_path" ]; then
+    echo "$command_path"
+  else
+    return 1
+  fi
+}
diff --git a/lib/commands/tmux-version.sh b/lib/commands/tmux-version.sh
new file mode 100644
index 0000000..ada850a
--- /dev/null
+++ b/lib/commands/tmux-version.sh
@@ -0,0 +1,63 @@
+# Enable extended globbing for version string cleanup.
+shopt -s extglob
+
+# Output current Tmux version, or compare against a target version.
+#
+# Usage:
+#   tmuxifier-tmux-version             # Outputs current Tmux version
+#   tmuxifier-tmux-version "1.9"       # Outputs "=", "<", or ">"
+#
+# Arguments:
+#   $1 - Optional target version to compare against
+#
+# Output:
+#   Without arguments: The current Tmux version string
+#   With target version: One of "=", "<", or ">" indicating if the current
+#                        Tmux version is equal to, less than, or greater than
+#                        the target version.
+#
+# Returns:
+#   0 - Always succeeds
+tmuxifier-tmux-version() {
+  # Provide tmuxifier help
+  if calling-help "$@"; then
+    echo "usage: tmuxifier tmux-version [<target-version>]
+
+Outputs current Tmux version. If given optional target-version it outputs one
+of three possible characters indicating if the current Tmux version number is
+equal to, less than, or greater than the <target-version>.
+
+The three possible outputs are \"=\", \"<\", and \">\"."
+    return
+  fi
+
+  local version
+  version="$(tmux -V)"
+  version="${version/tmux /}"
+
+  # Fix for tmux next-* versions
+  version="${version/next-/}"
+
+  if [ -z "$1" ]; then
+    echo "$version"
+    return
+  fi
+
+  if [ "$version" == "master" ]; then
+    # When version string is "master", tmux was compiled from source, and we
+    # assume it's later than whatever the <target-version> is.
+    echo '>'
+  else
+    # Fix for "1.9a" version comparison, as vercomp() can only deal with
+    # purely numeric version numbers.
+    version="${version//+([a-zA-Z])/}"
+
+    local result
+    vercomp "$version" "$1" && result=$? || result=$?
+    case $result in
+      0) echo '=' ;;
+      1) echo '>' ;;
+      2) echo '<' ;;
+    esac
+  fi
+}
diff --git a/lib/load.sh b/lib/load.sh
new file mode 100644
index 0000000..7a1b3af
--- /dev/null
+++ b/lib/load.sh
@@ -0,0 +1,17 @@
+# Setup layout path.
+if [ -z "${TMUXIFIER_LAYOUT_PATH}" ]; then
+  export TMUXIFIER_LAYOUT_PATH="${TMUXIFIER}/layouts"
+else
+  export TMUXIFIER_LAYOUT_PATH="${TMUXIFIER_LAYOUT_PATH%/}"
+fi
+
+# Add tmuxifier's internal commands to PATH.
+export PATH="$TMUXIFIER/libexec:$PATH"
+
+# Load utility functions.
+source "$TMUXIFIER/lib/util.sh"
+
+# Load command functions from lib/commands/ directory directly.
+source "$TMUXIFIER/lib/commands/alias.sh"
+source "$TMUXIFIER/lib/commands/resolve-command-path.sh"
+source "$TMUXIFIER/lib/commands/tmux-version.sh"
diff --git a/libexec/tmuxifier-alias b/libexec/tmuxifier-alias
index 60c63a2..329b416 100755
--- a/libexec/tmuxifier-alias
+++ b/libexec/tmuxifier-alias
@@ -1,47 +1,6 @@
 #! /usr/bin/env bash
-set -e
 [ -n "$TMUXIFIER_DEBUG" ] && set -x
 
-# Load internal utility functions.
-source "$TMUXIFIER/lib/util.sh"
+source "$TMUXIFIER/lib/load.sh"
 
-# Provide tmuxifier help
-if calling-help "$@"; then
-  echo "usage: tmuxifier alias <alias>
-
-Resolve a command alias to it's full name."
-  exit
-fi
-
-case "$1" in
-  "session" | "ses" | "s")
-    echo "load-session"
-    ;;
-  "window" | "win" | "w")
-    echo "load-window"
-    ;;
-  "new-ses" | "nses" | "ns")
-    echo "new-session"
-    ;;
-  "new-win" | "nwin" | "nw")
-    echo "new-window"
-    ;;
-  "edit-ses" | "eses" | "es")
-    echo "edit-session"
-    ;;
-  "edit-win" | "ewin" | "ew")
-    echo "edit-window"
-    ;;
-  "l")
-    echo "list"
-    ;;
-  "list-ses" | "lses" | "ls")
-    echo "list-sessions"
-    ;;
-  "list-win" | "lwin" | "lw")
-    echo "list-windows"
-    ;;
-  *)
-    exit 1
-    ;;
-esac
+tmuxifier-alias "$@"
diff --git a/libexec/tmuxifier-resolve-command-path b/libexec/tmuxifier-resolve-command-path
index 6eeec67..39be6db 100755
--- a/libexec/tmuxifier-resolve-command-path
+++ b/libexec/tmuxifier-resolve-command-path
@@ -1,30 +1,6 @@
 #! /usr/bin/env bash
-set -e
 [ -n "$TMUXIFIER_DEBUG" ] && set -x
 
-# Load internal utility functions.
-source "$TMUXIFIER/lib/util.sh"
+source "$TMUXIFIER/lib/load.sh"
 
-# Provide tmuxifier help
-if calling-help "$@"; then
-  echo "usage: tmuxifier resolve-command-path <command_or_alias>
-
-Outputs the absolute path to the given command or command alias."
-  exit
-fi
-
-if [ -n "$1" ]; then
-  ! command_path="$(command -v "tmuxifier-$1")"
-  if [ -z "$command_path" ]; then
-    resolved="$(tmuxifier-alias "$1")"
-    if [ -n "$resolved" ]; then
-      ! command_path="$(command -v "tmuxifier-$resolved")"
-    fi
-  fi
-fi
-
-if [ -n "$command_path" ]; then
-  echo "$command_path"
-else
-  exit 1
-fi
+tmuxifier-resolve-command-path "$@"
diff --git a/libexec/tmuxifier-tmux-version b/libexec/tmuxifier-tmux-version
index 8dedff5..89ace4e 100755
--- a/libexec/tmuxifier-tmux-version
+++ b/libexec/tmuxifier-tmux-version
@@ -1,70 +1,6 @@
 #! /usr/bin/env bash
-shopt -s extglob
 [ -n "$TMUXIFIER_DEBUG" ] && set -x
 
-# Load internal utility functions.
-source "$TMUXIFIER/lib/util.sh"
+source "$TMUXIFIER/lib/load.sh"
 
-# Provide tmuxifier help
-if calling-help "$@"; then
-  echo "usage: tmuxifier tmux-version [<target-version>]
-
-Outputs current Tmux version. If given optional target-version it outputs one
-of three possible characters indicating if the current Tmux version number is
-equal to, less than, or greater than the <target-version>.
-
-The three possible outputs are \"=\", \"<\", and \">\"."
-  exit
-fi
-
-# The vercomp() function is shamelessly ripped/borrowed from the following
-# StackOverflow answer: http://stackoverflow.com/a/4025065/42146
-vercomp() {
-  if [[ $1 == $2 ]]; then return 0; fi
-
-  local IFS=.
-  local i ver1=($1) ver2=($2)
-
-  # fill empty fields in ver1 with zeros
-  for ((i = ${#ver1[@]}; i < ${#ver2[@]}; i++)); do ver1[i]=0; done
-
-  for ((i = 0; i < ${#ver1[@]}; i++)); do
-    # fill empty fields in ver2 with zeros
-    if [[ -z ${ver2[i]} ]]; then ver2[i]=0; fi
-
-    if ((10#${ver1[i]} > 10#${ver2[i]})); then
-      return 1
-    elif ((10#${ver1[i]} < 10#${ver2[i]})); then
-      return 2
-    fi
-  done
-  return 0
-}
-
-version=$(tmux -V)
-version=${version/tmux /}
-
-# Fix for tmux next-* versions
-version=${version/next-/}
-
-if [ -z "$1" ]; then
-  echo "$version"
-  exit
-fi
-
-if [ "$version" == "master" ]; then
-  # When version string is "master", tmux was compiled from source, and we
-  # assume it's later than whatever the <target-version> is.
-  echo '>'
-else
-  # Fix for "1.9a" version comparison, as vercomp() can only deal with
-  # purely numeric version numbers.
-  version=${version//+([a-zA-Z])/}
-
-  vercomp "$version" "$1"
-  case $? in
-    0) echo '=' ;;
-    1) echo '>' ;;
-    2) echo '<' ;;
-  esac
-fi
+tmuxifier-tmux-version "$@"