diff --git a/src/main.rs b/src/main.rs
index 38f7cbe..85245d8 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -129,10 +129,11 @@ fn main() -> Result<(), std::io::Error> {
 							},
 							Err((l, e)) => {
 								write!(
-									stdout, "{}{}{} {e:?}{}\r\n",
+									stdout, "{}{}{} {}{}\r\n",
 									color::Fg(color::Red),
 									" ".repeat(l.pos + 4),
 									"^".repeat(l.len),
+									e.to_message(),
 									color::Fg(color::Reset),
 								)?;
 							}
diff --git a/src/parser.rs b/src/parser.rs
index e3e59bc..34a35ab 100644
--- a/src/parser.rs
+++ b/src/parser.rs
@@ -255,11 +255,37 @@ pub struct LineLocation {
 /// If we cannot parse a string, one of these is returned.
 #[derive(Debug)]
 pub enum ParserError {
-	MissingCloseParen,
+	//MissingCloseParen,
 	ExtraCloseParen,
 	EmptyGroup,
 	Syntax,
-	BadNumber 
+	Undefined(String),
+	BadNumber
+}
+
+impl ParserError {
+	pub fn to_message(&self) -> String {
+		match self {
+			//ParserError::MissingCloseParen => {
+			//	String::from("This group is never closed")
+			//},
+			ParserError::ExtraCloseParen => {
+				String::from("Extra close parenthesis")
+			},
+			ParserError::EmptyGroup => {
+				String::from("Groups can't be empty")
+			},
+			ParserError::Syntax => {
+				String::from("Syntax")
+			},
+			ParserError::Undefined(s) => {
+				format!("\"{s}\" isn't defined")
+			},
+			ParserError::BadNumber => {
+				String::from("Invalid number")
+			}
+		}
+	}
 }
 
 
diff --git a/src/parser/find_subs.rs b/src/parser/find_subs.rs
index 06ad1a8..ac2d9f4 100644
--- a/src/parser/find_subs.rs
+++ b/src/parser/find_subs.rs
@@ -34,7 +34,7 @@ pub fn p_find_subs(
 			},
 
 			Token::PreWord(_, s) => {
-				match &s[..] {
+				let target = match &s[..] {
 					// Greek letters
 					"alpha"   => {Some("α")},
 					"beta"    => {Some("β")},
@@ -62,7 +62,15 @@ pub fn p_find_subs(
 					"omega"   => {Some("ω")}
 
 					_ => {None}
+				};
+
+				// Update preword contents too.
+				// This makes sure future prints of this token
+				// contain substituted text too.
+				if target.is_some() {*
+					s = String::from(target.unwrap());
 				}
+				target
 			},
 
 			_ => {None}
diff --git a/src/parser/groupify.rs b/src/parser/groupify.rs
index 45058a4..279ccce 100644
--- a/src/parser/groupify.rs
+++ b/src/parser/groupify.rs
@@ -73,7 +73,7 @@ pub fn p_groupify(mut g: VecDeque<Token>) -> Result<Token, (LineLocation, Parser
 		let t = g.pop_front().unwrap();
 		let (l_now, v_now) = levels.last_mut().unwrap();
 
-		match &t {
+		match t {
 			Token::PreOperator(_, _) => {
 				v_now.push_back(t);
 				lookback(v_now)?;
@@ -82,23 +82,25 @@ pub fn p_groupify(mut g: VecDeque<Token>) -> Result<Token, (LineLocation, Parser
 			Token::PreNumber(l, s) => {
 				let n = match s.parse() {
 					Ok(n) => n,
-					Err(_) => return Err((*l, ParserError::BadNumber))
+					Err(_) => return Err((l, ParserError::BadNumber))
 				};
-				v_now.push_back(Token::Number(*l, n));
+				v_now.push_back(Token::Number(l, n));
 				lookback(v_now)?;
 			},
 
 			Token::PreWord(l, s) => {
+				// This method must support both plain text and
+				// unicode versions of each word.
 				v_now.push_back(match &s[..] {
-					"mod" => { Token::PreOperator(*l, Operator::ModuloLong) },
-					"pi" => { Token::Constant(*l, 3.141592653, String::from("π")) },
-					_ => { return Err((*l, ParserError::Syntax)); }
+					"mod" => { Token::PreOperator(l, Operator::ModuloLong) },
+					"π"|"pi" => { Token::Constant(l, 3.141592653, String::from("π")) },
+					_ => { return Err((l, ParserError::Undefined(s))); }
 				});
 				lookback(v_now)?;
 			},
 
 			Token::PreGroupStart(l) => {
-				levels.push((*l, VecDeque::with_capacity(8)));
+				levels.push((l, VecDeque::with_capacity(8)));
 				i_level += 1;
 			},
 
@@ -129,10 +131,28 @@ pub fn p_groupify(mut g: VecDeque<Token>) -> Result<Token, (LineLocation, Parser
 		}
 	}
 
+	/*
+	// Error on missing parenthesis
 	if levels.len() != 1 {
 		let (l, _) = levels.pop().unwrap();
 		return Err((l, ParserError::MissingCloseParen))
 	}
+	*/
+
+	// Auto-close parenthesis
+	while levels.len() != 1 {
+		let (l, v) = levels.pop().unwrap();
+		let (_, v_now) = levels.last_mut().unwrap();
+
+		// Catch empty groups
+		if v.len() == 0 {
+			return Err((l, ParserError::EmptyGroup))
+		}
+
+		v_now.push_back(Token::PreGroup(l, v));
+		lookback(v_now)?;
+	}
+
 
 	let (_, v) = levels.pop().unwrap();
 	return Ok(Token::PreGroup(LineLocation{pos:0, len:0}, v));
diff --git a/src/parser/tokenize.rs b/src/parser/tokenize.rs
index 56035c7..7a2bd5c 100644
--- a/src/parser/tokenize.rs
+++ b/src/parser/tokenize.rs
@@ -33,7 +33,6 @@ pub fn p_tokenize(input: &String) -> VecDeque<Token> {
 
 
 	for (i, c) in input.chars().enumerate() {
-
 		match c {
 			// The minus sign can be both a Negative and an Operator.
 			// Needs special treatment.
@@ -82,8 +81,8 @@ pub fn p_tokenize(input: &String) -> VecDeque<Token> {
 
 			// Operator
 			// Always one character
-			'*'|'/'|'+'|
-			'^'|'!'|'%'
+			'*'|'×'|'/'|'÷'|
+			'+'|'^'|'!'|'%'
 			=> {
 				if t.is_some() { g.push_back(update_line_location(t.unwrap(), i)); }
 				t = Some(Token::PreOperator(
@@ -136,7 +135,7 @@ pub fn p_tokenize(input: &String) -> VecDeque<Token> {
 		};
 	}
 
-	if t.is_some() { g.push_back(update_line_location(t.unwrap(), input.len())); }
+	if t.is_some() { g.push_back(update_line_location(t.unwrap(), input.chars().count())); }
 
 	return g;
 }
\ No newline at end of file