diff --git a/README.md b/README.md
index 34af473..8b0e350 100644
--- a/README.md
+++ b/README.md
@@ -213,6 +213,15 @@ Run `M-x customize-group RET doom-modeline RET` or set the variables.
 ;; The interval of checking github.
 (setq doom-modeline-github-interval (* 30 60))
 
+;; Whether display mu4e notifications or not. Requires `mu4e-alert' package.
+(setq doom-modeline-mu4e t)
+
+;; Whether display irc notifications or not. Requires `circe' package.
+(setq doom-modeline-irc t)
+
+;; Function to stylize the irc buffer names.
+(setq doom-modeline-irc-stylize 'identity)
+
 ;; Whether display environment version or not
 (setq doom-modeline-env-version t)
 ;; Or for individual languages
@@ -223,15 +232,6 @@ Run `M-x customize-group RET doom-modeline RET` or set the variables.
 (setq doom-modeline-env-enable-elixir t)
 (setq doom-modeline-env-enable-rust t)
 
-;; Whether display mu4e notifications or not. Requires `mu4e-alert' package.
-(setq doom-modeline-mu4e t)
-
-;; Whether display irc notifications or not. Requires `circe' package.
-(setq doom-modeline-irc t)
-
-;; Function to stylize the irc buffer names.
-(setq doom-modeline-irc-stylize 'identity)
-
 ;; Change the executables to use for the language version string
 (setq doom-modeline-env-python-executable "python") ; or `python-shell-interpreter'
 (setq doom-modeline-env-ruby-executable "ruby")
diff --git a/doom-modeline-env.el b/doom-modeline-env.el
index 1cdc9b4..b541003 100644
--- a/doom-modeline-env.el
+++ b/doom-modeline-env.el
@@ -30,6 +30,9 @@
 (require 'subr-x)
 (require 'doom-modeline-core)
 
+;; Externals
+(defvar python-shell-interpreter)
+
 ;;
 ;; Customizations
 ;;
@@ -38,37 +41,6 @@
   "The environment parser for doom-modeline."
   :group 'doom-modeline)
 
-(defcustom doom-modeline-env-python-executable
-  (or (bound-and-true-p python-shell-interpreter) "python")
-  "The executable to parse Python version."
-  :type 'string
-  :group 'doom-modeline-env)
-
-(defcustom doom-modeline-env-ruby-executable "ruby"
-  "The executable to parse Ruby version."
-  :type 'string
-  :group 'doom-modeline-env)
-
-(defcustom doom-modeline-env-perl-executable "perl"
-  "The executable to parse Perl version."
-  :type 'string
-  :group 'doom-modeline-env)
-
-(defcustom doom-modeline-env-go-executable "go"
-  "The executable to parse Golang version."
-  :type 'string
-  :group 'doom-modeline-env)
-
-(defcustom doom-modeline-env-elixir-executable "iex"
-  "The executable to parse Elixir version."
-  :type 'string
-  :group 'doom-modeline-env)
-
-(defcustom doom-modeline-env-rust-executable "rustc"
-  "The executable to parse Rust version."
-  :type 'string
-  :group 'doom-modeline-env)
-
 (defcustom doom-modeline-env-load-string "..."
   "What to dispaly as the version while a new one is being loaded."
   :type 'string
@@ -84,7 +56,6 @@
   :type 'hook
   :group 'doom-modeline-env)
 
-
 ;; Show version string for multi-version managers like rvm, rbenv, pyenv, etc.
 (defvar-local doom-modeline-env--version nil
   "The version to display with major-mode in mode-line.
@@ -222,16 +193,20 @@ PARSER should be a function for parsing COMMAND's output line-by-line, to
   :command (lambda () (cond ((and (fboundp 'pipenv-project-p)
                              (pipenv-project-p))
                         (list "pipenv" "run"
-                              doom-modeline-env-python-executable
+                              (or doom-modeline-env-python-executable
+                                  python-shell-interpreter
+                                  "python")
                               "--version"))
-                       ((list doom-modeline-env-python-executable
+                       ((list (or doom-modeline-env-python-executable
+                                  python-shell-interpreter
+                                  "python")
                               "--version"))))
   :parser  (lambda (line) (cadr (split-string line))))
 
 ;;;###autoload (autoload 'doom-modeline-env-setup-ruby "doom-modeline-env")
 (doom-modeline-def-env ruby
   :hooks   '(ruby-mode-hook enh-ruby-mode-hook)
-  :command (lambda () (list doom-modeline-env-ruby-executable "--version"))
+  :command (lambda () (list (or doom-modeline-env-ruby-executable "ruby") "--version"))
   :parser  (lambda (line)
              (car (split-string
                    (cadr
@@ -241,7 +216,7 @@ PARSER should be a function for parsing COMMAND's output line-by-line, to
 ;;;###autoload (autoload 'doom-modeline-env-setup-perl "doom-modeline-env")
 (doom-modeline-def-env perl
   :hooks   'perl-mode-hook
-  :command (lambda () (list doom-modeline-env-perl-executable "--version"))
+  :command (lambda () (list (or doom-modeline-env-perl-executable "perl") "--version"))
   :parser  (lambda (line)
              (cadr
               (split-string
@@ -255,7 +230,7 @@ PARSER should be a function for parsing COMMAND's output line-by-line, to
 ;;;###autoload (autoload 'doom-modeline-env-setup-go "doom-modeline-env")
 (doom-modeline-def-env go
   :hooks   'go-mode-hook
-  :command (lambda () (list doom-modeline-env-go-executable "version"))
+  :command (lambda () (list (or doom-modeline-env-go-executable "go") "version"))
   :parser  (lambda (line)
              (cadr
               (split-string
@@ -267,13 +242,13 @@ PARSER should be a function for parsing COMMAND's output line-by-line, to
 ;;;###autoload (autoload 'doom-modeline-env-setup-elixir "doom-modeline-env")
 (doom-modeline-def-env elixir
   :hooks   'elixir-mode-hook
-  :command (lambda () (list doom-modeline-env-elixir-executable "--version"))
+  :command (lambda () (list (or doom-modeline-env-elixir-executable "iex") "--version"))
   :parser  (lambda (line) (cadr (split-string line))))
 
 ;;;###autoload (autoload 'doom-modeline-env-setup-rust "doom-modeline-env")
 (doom-modeline-def-env rust
   :hooks   'rust-mode-hook
-  :command (lambda () (list doom-modeline-env-rust-executable "--version"))
+  :command (lambda () (list (or doom-modeline-env-rust-executable "rustc") "--version"))
   :parser  (lambda (line)
              (car
               (split-string