diff --git a/src/Expression.cpp b/src/Expression.cpp
index 495f28143..eb03ab371 100644
--- a/src/Expression.cpp
+++ b/src/Expression.cpp
@@ -34,6 +34,7 @@
 #include <Duration.h>
 #include <Nibbler.h>
 #include <Variant.h>
+#include <RegX.h>
 #include <text.h>
 #include <Expression.h>
 
@@ -199,39 +200,15 @@ bool Expression::eval (Task& task)
       else if (arg->first == "!~")
       {
 //        std::cout << "#   " << left.dump () << " !~ " << right.dump () << "\n";
-        bool result = false;
+        bool case_sensitive = context.config.getBoolean ("search.case.sensitive");
+        bool result = !eval_match (left, right, case_sensitive);
 
         // Matches against description are really against either description,
         // annotations or project.
-        if (left._raw == "description")
+        // Short-circuit if match already failed.
+        if (result && left._raw == "description")
         {
-          if (right._raw_type == "rx")
-          {
-            throw std::string ("rx not supported");
-          }
-          else
-          {
-            left.cast (Variant::v_string);
-            right.cast (Variant::v_string);
-            if (left._string.find (right._string) == std::string::npos)
-              result = true;
-          }
-        }
-
-        // Matches against non-description fields are treated as-is.
-        else
-        {
-          if (right._raw_type == "rx")
-          {
-            throw std::string ("rx not supported");
-          }
-          else
-          {
-            left.cast (Variant::v_string);
-            right.cast (Variant::v_string);
-            if (left._string.find (right._string) == std::string::npos)
-              result = true;
-          }
+          // TODO check further.
         }
 
         left = Variant (result);
@@ -277,39 +254,15 @@ bool Expression::eval (Task& task)
       else if (arg->first == "~")
       {
 //        std::cout << "#   " << left.dump () << " ~ " << right.dump () << "\n";
-        bool result = false;
+        bool case_sensitive = context.config.getBoolean ("search.case.sensitive");
+        bool result = eval_match (left, right, case_sensitive);
 
         // Matches against description are really against either description,
         // annotations or project.
-        if (left._raw == "description")
+        // Short-circuit if match is already found.
+        if (!result && left._raw == "description")
         {
-          if (right._raw_type == "rx")
-          {
-            throw std::string ("rx not supported");
-          }
-          else
-          {
-            left.cast (Variant::v_string);
-            right.cast (Variant::v_string);
-            if (left._string.find (right._string) != std::string::npos)
-              result = true;
-          }
-        }
-
-        // Matches against non-description fields are treated as-is.
-        else
-        {
-          if (right._raw_type == "rx")
-          {
-            throw std::string ("rx not supported");
-          }
-          else
-          {
-            left.cast (Variant::v_string);
-            right.cast (Variant::v_string);
-            if (left._string.find (right._string) != std::string::npos)
-              result = true;
-          }
+          // TODO check further.
         }
 
         left = Variant (result);
@@ -384,6 +337,32 @@ bool Expression::eval (Task& task)
   return pass_fail;
 }
 
+////////////////////////////////////////////////////////////////////////////////
+bool Expression::eval_match (Variant& left, Variant& right, bool case_sensitive)
+{
+  if (right._raw_type == "rx")
+  {
+    left.cast (Variant::v_string);
+    right.cast (Variant::v_string);
+
+    // Create a cached entry, if it does not already exist.
+    if (_regexes.find (right._string) == _regexes.end ())
+      _regexes[right._string] = RegX (right._string, case_sensitive);
+
+    if (_regexes[right._string].match (left._string))
+      return true;
+  }
+  else
+  {
+    left.cast (Variant::v_string);
+    right.cast (Variant::v_string);
+    if (find (left._string, right._string, (bool) case_sensitive) != std::string::npos)
+      return true;
+  }
+
+  return false;
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 void Expression::create_variant (
   Variant& variant,
diff --git a/src/Expression.h b/src/Expression.h
index 56767ad5a..b7d0a13f3 100644
--- a/src/Expression.h
+++ b/src/Expression.h
@@ -32,6 +32,7 @@
 #include <stack>
 #include <Arguments.h>
 #include <Task.h>
+#include <RegX.h>
 #include <Variant.h>
 
 class Expression
@@ -56,10 +57,11 @@ private:
   bool is_new_style ();
 
 private:
-
+  bool eval_match (Variant&, Variant&, bool);
 
 private:
   Arguments _args;
+  std::map <std::string, RegX> _regexes;
 };
 
 #endif
diff --git a/src/RegX.cpp b/src/RegX.cpp
index 151aa9064..0b2653cca 100644
--- a/src/RegX.cpp
+++ b/src/RegX.cpp
@@ -34,6 +34,14 @@
 //#define _POSIX_C_SOURCE 1
 #define MAX_MATCHES 64
 
+////////////////////////////////////////////////////////////////////////////////
+RegX::RegX ()
+: _compiled (false)
+, _pattern ("")
+, _case_sensitive (true)
+{
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 RegX::RegX (
   const std::string& pattern,
diff --git a/src/RegX.h b/src/RegX.h
index 067009d2d..d93a0883c 100644
--- a/src/RegX.h
+++ b/src/RegX.h
@@ -36,6 +36,7 @@
 class RegX
 {
 public:
+  RegX ();
   RegX (const std::string&, bool caseSensitive = true);
   RegX (const RegX&);
   RegX& operator= (const RegX&);