diff --git a/library/HTMLPurifier/VarParser.php b/library/HTMLPurifier/VarParser.php
index 1d07329a..bb0313f1 100644
--- a/library/HTMLPurifier/VarParser.php
+++ b/library/HTMLPurifier/VarParser.php
@@ -2,9 +2,9 @@
 
 /**
  * Parses string representations into their corresponding native PHP
- * variable type.
+ * variable type. The base implementation does a simple type-check.
  */
-abstract class HTMLPurifier_VarParser
+class HTMLPurifier_VarParser
 {
     
     /**
@@ -34,6 +34,81 @@ abstract class HTMLPurifier_VarParser
      * @param $allow_null Whether or not to permit null as a value
      * @return Validated and type-coerced variable
      */
-    abstract public function parse($var, $type, $allow_null = false);
+    final public function parse($var, $type, $allow_null = false) {
+        if (!isset(HTMLPurifier_VarParser::$types[$type])) {
+            throw new HTMLPurifier_VarParserException("Invalid type $type");
+        }
+        $var = $this->parseImplementation($var, $type, $allow_null);
+        if ($allow_null && $var === null) return null;
+        // These are basic checks, to make sure nothing horribly wrong
+        // happened in our implementations.
+        switch ($type) {
+            case 'string':
+            case 'istring':
+            case 'text':
+            case 'itext':
+                if (!is_string($var)) break;
+                if ($type[0] == 'i') $var = strtolower($var);
+                return $var;
+            case 'int':
+                if (!is_int($var)) break;
+                return $var;
+            case 'float':
+                if (!is_float($var)) break;
+                return $var;
+            case 'bool':
+                if (!is_bool($var)) break;
+                return $var;
+            case 'lookup':
+            case 'list':
+            case 'hash':
+                if (!is_array($var)) break;
+                if ($type === 'lookup') {
+                    foreach ($var as $k) if ($k !== true) $this->error('Lookup table contains value other than true');
+                } elseif ($type === 'list') {
+                    $keys = array_keys($var);
+                    if (array_keys($keys) !== $keys) $this->error('Indices for list are not uniform');
+                }
+                return $var;
+            case 'mixed':
+                return $var;
+            default:
+                $this->errorInconsistent(__CLASS__, $type);
+        }
+        $this->errorGeneric($var, $type);
+    }
+    
+    /**
+     * Actually implements the parsing. Base implementation is to not
+     * do anything to $var. Subclasses should overload this!
+     */
+    protected function parseImplementation($var, $type, $allow_null) {
+        return $var;
+    }
+    
+    /**
+     * Throws an exception.
+     */
+    protected function error($msg) {
+        throw new HTMLPurifier_VarParserException($msg);
+    }
+    
+    /**
+     * Throws an inconsistency exception.
+     * @note This should not ever be called. It would be called if we
+     *       extend the allowed values of HTMLPurifier_VarParser without
+     *       updating subclasses.
+     */
+    protected function errorInconsistent($class, $type) {
+        throw new HTMLPurifier_Exception("Inconsistency in $class: $type not implemented");
+    }
+    
+    /**
+     * Generic error for if a type didn't work.
+     */
+    protected function errorGeneric($var, $type) {
+        $vtype = gettype($var);
+        $this->error("Expected type $type, got $vtype");
+    }
     
 }
diff --git a/library/HTMLPurifier/VarParser/Flexible.php b/library/HTMLPurifier/VarParser/Flexible.php
index fcec974b..1c5ddcb7 100644
--- a/library/HTMLPurifier/VarParser/Flexible.php
+++ b/library/HTMLPurifier/VarParser/Flexible.php
@@ -8,31 +8,23 @@
 class HTMLPurifier_VarParser_Flexible extends HTMLPurifier_VarParser
 {
     
-    public function parse($var, $type, $allow_null = false) {
-        if (!isset(HTMLPurifier_VarParser::$types[$type])) {
-            throw new HTMLPurifier_VarParserException("Invalid type $type");
-        }
+    protected function parseImplementation($var, $type, $allow_null) {
         if ($allow_null && $var === null) return null;
         switch ($type) {
             // Note: if code "breaks" from the switch, it triggers a generic
             // exception to be thrown. Specific errors can be specifically
             // done here.
             case 'mixed':
-                return $var;
             case 'istring':
             case 'string':
-            case 'text': // no difference, just is longer/multiple line string
+            case 'text':
             case 'itext':
-                if (!is_string($var)) break;
-                if ($type === 'istring' || $type === 'itext') $var = strtolower($var);
                 return $var;
             case 'int':
                 if (is_string($var) && ctype_digit($var)) $var = (int) $var;
-                elseif (!is_int($var)) break;
                 return $var;
             case 'float':
                 if (is_string($var) && is_numeric($var)) $var = (float) $var;
-                elseif (!is_float($var)) break;
                 return $var;
             case 'bool':
                 if (is_int($var) && ($var === 0 || $var === 1)) {
@@ -45,7 +37,7 @@ class HTMLPurifier_VarParser_Flexible extends HTMLPurifier_VarParser
                     } else {
                         throw new HTMLPurifier_VarParserException("Unrecognized value '$var' for $type");
                     }
-                } elseif (!is_bool($var)) break;
+                }
                 return $var;
             case 'list':
             case 'hash':
@@ -94,10 +86,9 @@ class HTMLPurifier_VarParser_Flexible extends HTMLPurifier_VarParser
                 }
                 return $var;
             default:
-                // This should not happen!
-                throw new HTMLPurifier_Exception("Inconsistency in HTMLPurifier_VarParser_Flexible: $type is not implemented");
+                $this->errorInconsistent(__CLASS__, $type);
         }
-        throw new HTMLPurifier_VarParserException("Invalid input for type $type");
+        $this->errorGeneric($var, $type);
     }
     
 }