diff --git a/src/Arguments.cpp b/src/Arguments.cpp
index d8ce9acb4..1870c9506 100644
--- a/src/Arguments.cpp
+++ b/src/Arguments.cpp
@@ -154,7 +154,7 @@ void Arguments::capture (int argc, const char** argv)
     // be an absolute path, and Expression::expand_tokens would make a dog's
     // dinner out of it.
     std::vector <std::string> parts;
-    if (is_multipart (argv[i], parts) && i != 0)
+    if (i && is_multipart (argv[i], parts))
     {
       std::vector <std::string>::iterator part;
       for (part = parts.begin (); part != parts.end (); ++part)
@@ -731,7 +731,7 @@ bool Arguments::is_multipart (
   std::string part;
   while (n.getQuoted ('"', part)  ||
          n.getQuoted ('\'', part) ||
-         n.getQuoted ('/', part) ||
+//         n.getQuoted ('/', part)  ||   <--- this line breaks subst.
          n.getUntilWS (part))
   {
     n.skipWS ();
@@ -864,14 +864,14 @@ bool Arguments::is_subst (const std::string& input)
   Nibbler n (input);
   if (n.skip     ('/')       &&
       n.getUntil ('/', from) &&
+      from.length ()         &&
       n.skip     ('/')       &&
       n.getUntil ('/', to)   &&
       n.skip     ('/'))
   {
     n.skip ('g');
-    if (n.depleted ()                 &&
-        ! Directory (input).exists () &&   // Ouch - expensive call.
-        from.length ())
+    if (n.depleted () &&
+        ! Directory (input).exists ())    // Ouch - expensive call.
       return true;
   }
 
@@ -1376,6 +1376,14 @@ bool Arguments::extract_operator (
 }
 
 ////////////////////////////////////////////////////////////////////////////////
+// Almost all arguments are filters, except:
+//   subst
+//   program
+//   command
+//   rc
+//   override
+//
+// Special case: attr "limit" is ignored.
 Arguments Arguments::extract_read_only_filter ()
 {
   Arguments filter;
@@ -1389,7 +1397,6 @@ Arguments Arguments::extract_read_only_filter ()
         arg->_third == "rc"       ||
         arg->_third == "override")
     {
-      ;
     }
 
     // Included.
@@ -1424,6 +1431,10 @@ Arguments Arguments::extract_read_only_filter ()
 }
 
 ////////////////////////////////////////////////////////////////////////////////
+// A write filter includes id/uuid anywhere on the command line, but any other
+// filter elements must occur before the command.
+//
+// Special case: attr "limit" is ignored.
 Arguments Arguments::extract_write_filter ()
 {
   Arguments filter;
@@ -1441,7 +1452,6 @@ Arguments Arguments::extract_write_filter ()
              arg->_third == "rc"       ||
              arg->_third == "override")
     {
-      ;
     }
 
     // Included regardless of position.
@@ -1471,10 +1481,13 @@ Arguments Arguments::extract_write_filter ()
     // Error.
     else
     {
-      // substitution
-      throw std::string ("A substitution '")
-            + arg->_first
-            + "' is not allowed in a read-only command filter.";
+      if (before_command)
+      {
+        // substitution
+        throw std::string ("A substitution '")
+              + arg->_first
+              + "' is not allowed in a write command filter.";
+      }
     }
   }
 
@@ -1574,13 +1587,13 @@ Arguments Arguments::extract_simple_words ()
     }
 
     // Included.
-    else if (arg->_third == "tag"          ||
-             arg->_third == "pattern"      ||
-             arg->_third == "substitution" ||
-             arg->_third == "id"           ||
-             arg->_third == "uuid"         ||
-             arg->_third == "op"           ||
-             arg->_third == "exp"          ||
+    else if (arg->_third == "tag"     ||
+             arg->_third == "pattern" ||
+             arg->_third == "subst"   ||
+             arg->_third == "id"      ||
+             arg->_third == "uuid"    ||
+             arg->_third == "op"      ||
+             arg->_third == "exp"     ||
              arg->_third == "word")
     {
       // "limit" is special - it is recognized but not included in filters.
diff --git a/src/Context.cpp b/src/Context.cpp
index a694516df..99b21751c 100644
--- a/src/Context.cpp
+++ b/src/Context.cpp
@@ -119,8 +119,7 @@ int Context::initialize (int argc, const char** argv)
     // Instantiate built-in column objects.
     Column::factory (columns);
 
-    // Categorize all arguments one more time.
-    // TODO This may not be necessary.
+    // Categorize all arguments one more time.  THIS IS NECESSARY.
     args.categorize ();
 
     // Handle default command and assumed 'info' command.
diff --git a/src/Task.cpp b/src/Task.cpp
index dc6c72bc0..0238433bd 100644
--- a/src/Task.cpp
+++ b/src/Task.cpp
@@ -861,8 +861,11 @@ void Task::substitute (
     }
   }
 
-  set ("description", description);
-  setAnnotations (annotations);
+  if (changes)
+  {
+    set ("description", description);
+    setAnnotations (annotations);
+  }
 }
 
 ////////////////////////////////////////////////////////////////////////////////
diff --git a/test/args.2.t b/test/args.2.t
new file mode 100755
index 000000000..76f760f76
--- /dev/null
+++ b/test/args.2.t
@@ -0,0 +1,83 @@
+#! /usr/bin/perl
+################################################################################
+## taskwarrior - a command line task list manager.
+##
+## Copyright 2006 - 2011, Paul Beckingham, Federico Hernandez.
+## All rights reserved.
+##
+## This program is free software; you can redistribute it and/or modify it under
+## the terms of the GNU General Public License as published by the Free Software
+## Foundation; either version 2 of the License, or (at your option) any later
+## version.
+##
+## This program is distributed in the hope that it will be useful, but WITHOUT
+## ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+## FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
+## details.
+##
+## You should have received a copy of the GNU General Public License along with
+## this program; if not, write to the
+##
+##     Free Software Foundation, Inc.,
+##     51 Franklin Street, Fifth Floor,
+##     Boston, MA
+##     02110-1301
+##     USA
+##
+################################################################################
+
+use strict;
+use warnings;
+use Test::More tests => 10;
+
+# Create the rc file.
+if (open my $fh, '>', 'args.rc')
+{
+  print $fh "data.location=.\n",
+            "confirmation=off\n";
+  close $fh;
+  ok (-r 'args.rc', 'Created args.rc');
+}
+
+# Test 'done' with en-passant changes.
+qx{../src/task rc:args.rc add one};
+qx{../src/task rc:args.rc add two};
+qx{../src/task rc:args.rc add three};
+qx{../src/task rc:args.rc add four};
+qx{../src/task rc:args.rc add five};
+
+qx{../src/task rc:args.rc 1 done oneanno};
+my $output = qx{../src/task rc:args.rc 1 info};
+like ($output, qr/oneanno/, 'done enpassant anno');
+
+qx{../src/task rc:args.rc 2 done /two/TWO/};
+$output = qx{../src/task rc:args.rc 2 info};
+like ($output, qr/Description\s+TWO/, 'done enpassant subst');
+
+qx{../src/task rc:args.rc 3 done +threetag};
+$output = qx{../src/task rc:args.rc 3 info};
+like ($output, qr/Tags\s+threetag/, 'done enpassant tag');
+
+qx{../src/task rc:args.rc 4 done pri:H};
+$output = qx{../src/task rc:args.rc 4 info};
+like ($output, qr/Priority\s+H/, 'done enpassant priority');
+
+qx{../src/task rc:args.rc 5 done pro:A};
+$output = qx{../src/task rc:args.rc 5 info};
+like ($output, qr/Project\s+A/, 'done enpassant project');
+
+# Cleanup.
+unlink 'pending.data';
+ok (!-r 'pending.data', 'Removed pending.data');
+
+unlink 'completed.data';
+ok (!-r 'completed.data', 'Removed completed.data');
+
+unlink 'undo.data';
+ok (!-r 'undo.data', 'Removed undo.data');
+
+unlink 'args.rc';
+ok (!-r 'args.rc', 'Removed args.rc');
+
+exit 0;
+
diff --git a/test/args.3.t b/test/args.3.t
new file mode 100755
index 000000000..90c533ae6
--- /dev/null
+++ b/test/args.3.t
@@ -0,0 +1,83 @@
+#! /usr/bin/perl
+################################################################################
+## taskwarrior - a command line task list manager.
+##
+## Copyright 2006 - 2011, Paul Beckingham, Federico Hernandez.
+## All rights reserved.
+##
+## This program is free software; you can redistribute it and/or modify it under
+## the terms of the GNU General Public License as published by the Free Software
+## Foundation; either version 2 of the License, or (at your option) any later
+## version.
+##
+## This program is distributed in the hope that it will be useful, but WITHOUT
+## ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+## FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
+## details.
+##
+## You should have received a copy of the GNU General Public License along with
+## this program; if not, write to the
+##
+##     Free Software Foundation, Inc.,
+##     51 Franklin Street, Fifth Floor,
+##     Boston, MA
+##     02110-1301
+##     USA
+##
+################################################################################
+
+use strict;
+use warnings;
+use Test::More tests => 10;
+
+# Create the rc file.
+if (open my $fh, '>', 'args.rc')
+{
+  print $fh "data.location=.\n",
+            "confirmation=off\n";
+  close $fh;
+  ok (-r 'args.rc', 'Created args.rc');
+}
+
+# Test 'delete' with en-passant changes.
+qx{../src/task rc:args.rc add one};
+qx{../src/task rc:args.rc add two};
+qx{../src/task rc:args.rc add three};
+qx{../src/task rc:args.rc add four};
+qx{../src/task rc:args.rc add five};
+
+qx{../src/task rc:args.rc 1 delete oneanno};
+my $output = qx{../src/task rc:args.rc 1 info};
+like ($output, qr/oneanno/, 'delete enpassant anno');
+
+qx{../src/task rc:args.rc 2 delete /two/TWO/};
+$output = qx{../src/task rc:args.rc 2 info};
+like ($output, qr/Description\s+TWO/, 'delete enpassant subst');
+
+qx{../src/task rc:args.rc 3 delete +threetag};
+$output = qx{../src/task rc:args.rc 3 info};
+like ($output, qr/Tags\s+threetag/, 'delete enpassant tag');
+
+qx{../src/task rc:args.rc 4 delete pri:H};
+$output = qx{../src/task rc:args.rc 4 info};
+like ($output, qr/Priority\s+H/, 'delete enpassant priority');
+
+qx{../src/task rc:args.rc 5 delete pro:A};
+$output = qx{../src/task rc:args.rc 5 info};
+like ($output, qr/Project\s+A/, 'delete enpassant project');
+
+# Cleanup.
+unlink 'pending.data';
+ok (!-r 'pending.data', 'Removed pending.data');
+
+unlink 'completed.data';
+ok (!-r 'completed.data', 'Removed completed.data');
+
+unlink 'undo.data';
+ok (!-r 'undo.data', 'Removed undo.data');
+
+unlink 'args.rc';
+ok (!-r 'args.rc', 'Removed args.rc');
+
+exit 0;
+
diff --git a/test/args.4.t b/test/args.4.t
new file mode 100755
index 000000000..e1f89501d
--- /dev/null
+++ b/test/args.4.t
@@ -0,0 +1,83 @@
+#! /usr/bin/perl
+################################################################################
+## taskwarrior - a command line task list manager.
+##
+## Copyright 2006 - 2011, Paul Beckingham, Federico Hernandez.
+## All rights reserved.
+##
+## This program is free software; you can redistribute it and/or modify it under
+## the terms of the GNU General Public License as published by the Free Software
+## Foundation; either version 2 of the License, or (at your option) any later
+## version.
+##
+## This program is distributed in the hope that it will be useful, but WITHOUT
+## ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+## FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
+## details.
+##
+## You should have received a copy of the GNU General Public License along with
+## this program; if not, write to the
+##
+##     Free Software Foundation, Inc.,
+##     51 Franklin Street, Fifth Floor,
+##     Boston, MA
+##     02110-1301
+##     USA
+##
+################################################################################
+
+use strict;
+use warnings;
+use Test::More tests => 10;
+
+# Create the rc file.
+if (open my $fh, '>', 'args.rc')
+{
+  print $fh "data.location=.\n",
+            "confirmation=off\n";
+  close $fh;
+  ok (-r 'args.rc', 'Created args.rc');
+}
+
+# Test 'start' with en-passant changes.
+qx{../src/task rc:args.rc add one};
+qx{../src/task rc:args.rc add two};
+qx{../src/task rc:args.rc add three};
+qx{../src/task rc:args.rc add four};
+qx{../src/task rc:args.rc add five};
+
+qx{../src/task rc:args.rc 1 start oneanno};
+my $output = qx{../src/task rc:args.rc 1 info};
+like ($output, qr/oneanno/, 'start enpassant anno');
+
+qx{../src/task rc:args.rc 2 start /two/TWO/};
+$output = qx{../src/task rc:args.rc 2 info};
+like ($output, qr/Description\s+TWO/, 'start enpassant subst');
+
+qx{../src/task rc:args.rc 3 start +threetag};
+$output = qx{../src/task rc:args.rc 3 info};
+like ($output, qr/Tags\s+threetag/, 'start enpassant tag');
+
+qx{../src/task rc:args.rc 4 start pri:H};
+$output = qx{../src/task rc:args.rc 4 info};
+like ($output, qr/Priority\s+H/, 'start enpassant priority');
+
+qx{../src/task rc:args.rc 5 start pro:A};
+$output = qx{../src/task rc:args.rc 5 info};
+like ($output, qr/Project\s+A/, 'start enpassant project');
+
+# Cleanup.
+unlink 'pending.data';
+ok (!-r 'pending.data', 'Removed pending.data');
+
+unlink 'completed.data';
+ok (!-r 'completed.data', 'Removed completed.data');
+
+unlink 'undo.data';
+ok (!-r 'undo.data', 'Removed undo.data');
+
+unlink 'args.rc';
+ok (!-r 'args.rc', 'Removed args.rc');
+
+exit 0;
+
diff --git a/test/args.5.t b/test/args.5.t
new file mode 100755
index 000000000..bcef61bc0
--- /dev/null
+++ b/test/args.5.t
@@ -0,0 +1,83 @@
+#! /usr/bin/perl
+################################################################################
+## taskwarrior - a command line task list manager.
+##
+## Copyright 2006 - 2011, Paul Beckingham, Federico Hernandez.
+## All rights reserved.
+##
+## This program is free software; you can redistribute it and/or modify it under
+## the terms of the GNU General Public License as published by the Free Software
+## Foundation; either version 2 of the License, or (at your option) any later
+## version.
+##
+## This program is distributed in the hope that it will be useful, but WITHOUT
+## ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+## FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
+## details.
+##
+## You should have received a copy of the GNU General Public License along with
+## this program; if not, write to the
+##
+##     Free Software Foundation, Inc.,
+##     51 Franklin Street, Fifth Floor,
+##     Boston, MA
+##     02110-1301
+##     USA
+##
+################################################################################
+
+use strict;
+use warnings;
+use Test::More tests => 10;
+
+# Create the rc file.
+if (open my $fh, '>', 'args.rc')
+{
+  print $fh "data.location=.\n",
+            "confirmation=off\n";
+  close $fh;
+  ok (-r 'args.rc', 'Created args.rc');
+}
+
+# Test 'stop' with en-passant changes.
+qx{../src/task rc:args.rc add one};
+qx{../src/task rc:args.rc add two};
+qx{../src/task rc:args.rc add three};
+qx{../src/task rc:args.rc add four};
+qx{../src/task rc:args.rc add five};
+
+qx{../src/task rc:args.rc 1 stop oneanno};
+my $output = qx{../src/task rc:args.rc 1 info};
+like ($output, qr/oneanno/, 'stop enpassant anno');
+
+qx{../src/task rc:args.rc 2 stop /two/TWO/};
+$output = qx{../src/task rc:args.rc 2 info};
+like ($output, qr/Description\s+TWO/, 'stop enpassant subst');
+
+qx{../src/task rc:args.rc 3 stop +threetag};
+$output = qx{../src/task rc:args.rc 3 info};
+like ($output, qr/Tags\s+threetag/, 'stop enpassant tag');
+
+qx{../src/task rc:args.rc 4 stop pri:H};
+$output = qx{../src/task rc:args.rc 4 info};
+like ($output, qr/Priority\s+H/, 'stop enpassant priority');
+
+qx{../src/task rc:args.rc 5 stop pro:A};
+$output = qx{../src/task rc:args.rc 5 info};
+like ($output, qr/Project\s+A/, 'stop enpassant project');
+
+# Cleanup.
+unlink 'pending.data';
+ok (!-r 'pending.data', 'Removed pending.data');
+
+unlink 'completed.data';
+ok (!-r 'completed.data', 'Removed completed.data');
+
+unlink 'undo.data';
+ok (!-r 'undo.data', 'Removed undo.data');
+
+unlink 'args.rc';
+ok (!-r 'args.rc', 'Removed args.rc');
+
+exit 0;
+