diff --git a/README.md b/README.md
index 54eec2d..756c5db 100644
--- a/README.md
+++ b/README.md
@@ -338,10 +338,10 @@ The following constants are defined by default:
 
 Name    | PHP constant
 ------- | ------------
-dirsep  | DIRECTORY_SEPARATOR
-homedir | $_SERVER['HOME']
-ln      | PHP_EOL
-pi      | M_PI
+DIRSEP  | DIRECTORY_SEPARATOR
+HOME    | $_SERVER['HOME']
+EOL     | PHP_EOL
+PI      | M_PI
 
 ## Extending
 
diff --git a/mad/calc.mad b/mad/calc.mad
index 6e6ef80..4ddd44a 100644
--- a/mad/calc.mad
+++ b/mad/calc.mad
@@ -41,14 +41,14 @@
         ((first cmd) args))))))
 
 ;; Define a file for readline and load it
-(def readlineFile (str homedir "calc_history"))
+(def readlineFile (str HOME "calc_history"))
 (readlineLoad readlineFile)
 
 ;; Main loop: Read input from user, add it to readline, and parse it
 (def mainLoop (fn () (let (inp (readline "> "))
   (do (readlineAdd inp)
     (readlineSave readlineFile)
-    (print (str (parseInput inp) "\n"))
+    (print (str (parseInput inp) EOL))
     true))))
 
 ;; Run it
diff --git a/src/Lib/IO.php b/src/Lib/IO.php
index 5acaca3..146fb67 100644
--- a/src/Lib/IO.php
+++ b/src/Lib/IO.php
@@ -8,8 +8,8 @@ class IO implements ILib
 {
     public function register(Env $env): void
     {
-        $env->set('dirsep', \DIRECTORY_SEPARATOR);
-        $env->set('homedir', $_SERVER['HOME'] . \DIRECTORY_SEPARATOR);
+        $env->set('DIRSEP', \DIRECTORY_SEPARATOR);
+        $env->set('HOME', $_SERVER['HOME'] . \DIRECTORY_SEPARATOR);
 
         $env->set('wd', new CoreFunc('wd', 'Get the current working directory.', 0, 0,
             fn () => getcwd() . \DIRECTORY_SEPARATOR
diff --git a/src/Lib/Math.php b/src/Lib/Math.php
index f1f92b3..ca0ab60 100644
--- a/src/Lib/Math.php
+++ b/src/Lib/Math.php
@@ -10,7 +10,7 @@ class Math implements ILib
     {
         // Constants
 
-        $env->set('pi', \M_PI);
+        $env->set('PI', \M_PI);
 
         // Basic arithmetic
 
diff --git a/src/Lib/Strings.php b/src/Lib/Strings.php
index d94643b..49791e5 100644
--- a/src/Lib/Strings.php
+++ b/src/Lib/Strings.php
@@ -9,7 +9,7 @@ class Strings implements ILib
 {
     public function register(Env $env): void
     {
-        $env->set('ln', \PHP_EOL);
+        $env->set('EOL', \PHP_EOL);
 
         $env->set('trim', new CoreFunc('trim', 'Remove whitespace from beginning and end of string.', 1, 1,
             fn (string $a) => trim($a)