diff --git a/src/main/kotlin/gay/pizza/pork/eval/Scope.kt b/src/main/kotlin/gay/pizza/pork/eval/Scope.kt
index 78e7a6a..14fdb60 100644
--- a/src/main/kotlin/gay/pizza/pork/eval/Scope.kt
+++ b/src/main/kotlin/gay/pizza/pork/eval/Scope.kt
@@ -5,7 +5,7 @@ class Scope(val parent: Scope? = null) {
 
   fun define(name: String, value: Any) {
     if (variables.containsKey(name)) {
-      throw RuntimeException("Variable '${name}' is already defined.")
+      throw RuntimeException("Variable '${name}' is already defined")
     }
     variables[name] = value
   }
@@ -24,7 +24,7 @@ class Scope(val parent: Scope? = null) {
   fun call(name: String, arguments: Arguments): Any {
     val value = value(name)
     if (value !is CallableFunction) {
-      throw RuntimeException("$value is not callable.")
+      throw RuntimeException("$value is not callable")
     }
     return value.call(arguments)
   }
@@ -35,7 +35,7 @@ class Scope(val parent: Scope? = null) {
 
   fun leave(): Scope {
     if (parent == null) {
-      throw RuntimeException("Parent context not found.")
+      throw RuntimeException("Parent context not found")
     }
     return parent
   }
diff --git a/src/main/kotlin/gay/pizza/pork/parse/TokenType.kt b/src/main/kotlin/gay/pizza/pork/parse/TokenType.kt
index 3b879e5..36a4bb3 100644
--- a/src/main/kotlin/gay/pizza/pork/parse/TokenType.kt
+++ b/src/main/kotlin/gay/pizza/pork/parse/TokenType.kt
@@ -4,8 +4,8 @@ import gay.pizza.pork.parse.TokenTypeProperty.*
 import gay.pizza.pork.parse.TokenFamily.*
 
 enum class TokenType(vararg properties: TokenTypeProperty) {
-  Symbol(SymbolFamily),
-  IntLiteral(NumericLiteralFamily),
+  Symbol(SymbolFamily, CharConsumer { (it in 'a'..'z') || (it in 'A'..'Z') || it == '_' }, KeywordUpgrader),
+  IntLiteral(NumericLiteralFamily, CharConsumer { it in '0'..'9' }),
   StringLiteral(StringLiteralFamily),
   Equality(OperatorFamily),
   Inequality(OperatorFamily),
@@ -28,7 +28,7 @@ enum class TokenType(vararg properties: TokenTypeProperty) {
   If(Keyword("if"), KeywordFamily),
   Then(Keyword("then"), KeywordFamily),
   Else(Keyword("else"), KeywordFamily),
-  Whitespace,
+  Whitespace(CharConsumer { it == ' ' || it == '\r' || it == '\n' || it == '\t' }),
   BlockComment(CommentFamily),
   LineComment(CommentFamily),
   EndOfFile;
@@ -38,9 +38,12 @@ enum class TokenType(vararg properties: TokenTypeProperty) {
   val singleChar: SingleChar? = properties.filterIsInstance<SingleChar>().singleOrNull()
   val family: TokenFamily =
     properties.filterIsInstance<TokenFamily>().singleOrNull() ?: OtherFamily
+  val charConsumer: CharConsumer? = properties.filterIsInstance<CharConsumer>().singleOrNull()
+  val tokenUpgrader: TokenUpgrader? = properties.filterIsInstance<TokenUpgrader>().singleOrNull()
 
   companion object {
     val Keywords = entries.filter { item -> item.keyword != null }
     val SingleChars = entries.filter { item -> item.singleChar != null }
+    val CharConsumers = entries.filter { item -> item.charConsumer != null }
   }
 }
diff --git a/src/main/kotlin/gay/pizza/pork/parse/TokenTypeProperty.kt b/src/main/kotlin/gay/pizza/pork/parse/TokenTypeProperty.kt
index 1f22f60..57278f6 100644
--- a/src/main/kotlin/gay/pizza/pork/parse/TokenTypeProperty.kt
+++ b/src/main/kotlin/gay/pizza/pork/parse/TokenTypeProperty.kt
@@ -4,4 +4,17 @@ interface TokenTypeProperty {
   class SingleChar(val char: Char) : TokenTypeProperty
   class Promotion(val nextChar: Char, val type: TokenType) : TokenTypeProperty
   class Keyword(val text: String) : TokenTypeProperty
+  class CharConsumer(val isValid: (Char) -> Boolean) : TokenTypeProperty
+  open class TokenUpgrader(val maybeUpgrade: (Token) -> Token?) : TokenTypeProperty
+
+  object KeywordUpgrader : TokenUpgrader({ token ->
+    var upgraded: Token? = null
+    for (item in TokenType.Keywords) {
+      if (item.keyword != null && token.text == item.keyword.text) {
+        upgraded = Token(item, token.start, token.text)
+        break
+      }
+    }
+    upgraded
+  })
 }
diff --git a/src/main/kotlin/gay/pizza/pork/parse/Tokenizer.kt b/src/main/kotlin/gay/pizza/pork/parse/Tokenizer.kt
index 440b890..eaff0eb 100644
--- a/src/main/kotlin/gay/pizza/pork/parse/Tokenizer.kt
+++ b/src/main/kotlin/gay/pizza/pork/parse/Tokenizer.kt
@@ -3,54 +3,6 @@ package gay.pizza.pork.parse
 class Tokenizer(val source: CharSource) {
   private var tokenStart: Int = 0
 
-  private fun isSymbol(c: Char): Boolean =
-    (c in 'a'..'z') || (c in 'A'..'Z') || c == '_'
-
-  private fun isDigit(c: Char): Boolean =
-    c in '0'..'9'
-
-  private fun isWhitespace(c: Char): Boolean =
-    c == ' ' || c == '\r' || c == '\n' || c == '\t'
-
-  private fun readSymbolOrKeyword(firstChar: Char): Token {
-    val symbol = buildString {
-      append(firstChar)
-      while (isSymbol(source.peek())) {
-        append(source.next())
-      }
-    }
-
-    var type = TokenType.Symbol
-    for (keyword in TokenType.Keywords) {
-      if (symbol == keyword.keyword?.text) {
-        type = keyword
-      }
-    }
-
-    return Token(type, tokenStart, symbol)
-  }
-
-  private fun readIntLiteral(firstChar: Char): Token {
-    val number = buildString {
-      append(firstChar)
-      while (isDigit(source.peek())) {
-        append(source.next())
-      }
-    }
-    return Token(TokenType.IntLiteral, tokenStart, number)
-  }
-
-  private fun readWhitespace(firstChar: Char): Token {
-    val whitespace = buildString {
-      append(firstChar)
-      while (isWhitespace(source.peek())) {
-        val char = source.next()
-        append(char)
-      }
-    }
-    return Token(TokenType.Whitespace, tokenStart, whitespace)
-  }
-
   private fun readBlockComment(firstChar: Char): Token {
     val comment = buildString {
       append(firstChar)
@@ -138,16 +90,24 @@ class Tokenizer(val source: CharSource) {
         return Token(type, tokenStart, text)
       }
 
-      if (isWhitespace(char)) {
-        return readWhitespace(char)
-      }
+      for (item in TokenType.CharConsumers) {
+        val consumer = item.charConsumer ?: continue
+        if (!consumer.isValid(char)) {
+          continue
+        }
 
-      if (isDigit(char)) {
-        return readIntLiteral(char)
-      }
-
-      if (isSymbol(char)) {
-        return readSymbolOrKeyword(char)
+        val text = buildString {
+          append(char)
+          while (consumer.isValid(source.peek())) {
+            append(source.next())
+          }
+        }
+        var token = Token(item, tokenStart, text)
+        val tokenUpgrader = item.tokenUpgrader
+        if (tokenUpgrader != null) {
+          token = tokenUpgrader.maybeUpgrade(token) ?: token
+        }
+        return token
       }
 
       if (char == '"') {