diff -up Data-FormValidator-4.66/lib/Data/FormValidator/Results.pm.orig Data-FormValidator-4.66/lib/Data/FormValidator/Results.pm
--- Data-FormValidator-4.66/lib/Data/FormValidator/Results.pm.orig	2010-02-24 15:31:03.000000000 +0100
+++ Data-FormValidator-4.66/lib/Data/FormValidator/Results.pm	2011-08-28 08:26:22.000000000 +0200
@@ -807,7 +807,7 @@ sub _create_sub_from_RE {
             # With methods, the value is the second argument
             my $val = $force_method_p ? $_[1] : $_[0];
             my ($match) = scalar ($val =~ $re);
-            if ($untaint_this && defined $match) {
+            if ($untaint_this && $match) {
                 # pass the value through a RE that matches anything to untaint it.
                 my ($untainted) = ($&  =~ m/(.*)/s);
                 return $untainted;
diff -up Data-FormValidator-4.66/t/untaint_match_check.t.orig Data-FormValidator-4.66/t/untaint_match_check.t
--- Data-FormValidator-4.66/t/untaint_match_check.t.orig	2011-08-28 08:26:54.000000000 +0200
+++ Data-FormValidator-4.66/t/untaint_match_check.t	2011-08-28 08:26:30.000000000 +0200
@@ -0,0 +1,22 @@
+use strict;
+use warnings;
+
+use Test::More tests => 3;
+
+use Data::FormValidator;
+
+"unrelated match" =~ /match/;
+
+my $result = Data::FormValidator->check(
+    { a => 'invalid value' },    # input data
+    {                            # validation profile
+        untaint_all_constraints => 1,
+        optional                => ['a'],
+        constraints             => { a => qr/never matches/, },
+    },
+);
+
+ok( not $result->success )
+    or diag( 'Valid: ', $result->valid );
+ok( $result->has_invalid );
+is_deeply( scalar($result->invalid), { 'a' => [ qr/never matches/ ] } );