diff --git a/doc/src/sgml/installation.sgml b/doc/src/sgml/installation.sgml
index 8400ce5d70b..b2d6990f783 100644
--- a/doc/src/sgml/installation.sgml
+++ b/doc/src/sgml/installation.sgml
@@ -2601,8 +2601,8 @@ cc-1020 cc: ERROR File = pqcomm.c, Line = 427
    <para>
      To build 64 bit binaries using MinGW, install the 64 bit tool set
      from <ulink url="http://mingw-w64.sourceforge.net/"></ulink>, put its bin
-     directory in the <envar>PATH</envar>, and run 
-     <command>configure</command> with the  
+     directory in the <envar>PATH</envar>, and run
+     <command>configure</command> with the
      <command>--host=x86_64-w64-mingw</command> option.
    </para>
 
diff --git a/doc/src/sgml/plhandler.sgml b/doc/src/sgml/plhandler.sgml
index 6cddf002fbe..20021bce650 100644
--- a/doc/src/sgml/plhandler.sgml
+++ b/doc/src/sgml/plhandler.sgml
@@ -216,6 +216,15 @@ CREATE LANGUAGE plsample
     should execute this code and return.
    </para>
 
+   <para>
+    It's recommended that you wrap all these function declarations,
+    as well as the <command>CREATE LANGUAGE</> command itself, into
+    an <firstterm>extension</> so that a simple <command>CREATE EXTENSION</>
+    command is sufficient to install the language.  See
+    <xref linkend="extend-extensions"> for information about writing
+    extensions.
+   </para>
+
    <para>
     The procedural languages included in the standard distribution
     are good references when trying to write your own language handler.
diff --git a/doc/src/sgml/plperl.sgml b/doc/src/sgml/plperl.sgml
index a481accd868..16984aab634 100644
--- a/doc/src/sgml/plperl.sgml
+++ b/doc/src/sgml/plperl.sgml
@@ -27,6 +27,7 @@
 
   <para>
    To install PL/Perl in a particular database, use
+   <literal>CREATE EXTENSION plperl</>, or from the shell command line use
    <literal>createlang plperl <replaceable>dbname</></literal>.
   </para>
 
@@ -127,9 +128,9 @@ $$ LANGUAGE plperl;
 
   <note>
     <para>
-      Arguments will be converted from the database's encoding to UTF-8 
-      for use inside plperl, and then converted from UTF-8 back to the 
-      database encoding upon return. 
+      Arguments will be converted from the database's encoding to UTF-8
+      for use inside plperl, and then converted from UTF-8 back to the
+      database encoding upon return.
     </para>
   </note>
 
@@ -967,8 +968,7 @@ $$ LANGUAGE plperl;
    mail.  To handle these cases, PL/Perl can also be installed as an
    <quote>untrusted</> language (usually called
    <application>PL/PerlU</application><indexterm><primary>PL/PerlU</></indexterm>).
-   In this case the full Perl language is available.  If the
-   <command>createlang</command> program is used to install the
+   In this case the full Perl language is available.  When installing the
    language, the language name <literal>plperlu</literal> will select
    the untrusted PL/Perl variant.
   </para>
diff --git a/doc/src/sgml/plpython.sgml b/doc/src/sgml/plpython.sgml
index a729fa3e177..0aa5159e2b7 100644
--- a/doc/src/sgml/plpython.sgml
+++ b/doc/src/sgml/plpython.sgml
@@ -14,6 +14,7 @@
 
  <para>
   To install PL/Python in a particular database, use
+  <literal>CREATE EXTENSION plpythonu</>, or from the shell command line use
   <literal>createlang plpythonu <replaceable>dbname</></literal> (but
   see also <xref linkend="plpython-python23">).
  </para>
diff --git a/doc/src/sgml/pltcl.sgml b/doc/src/sgml/pltcl.sgml
index 052a158fa98..4215f192ba5 100644
--- a/doc/src/sgml/pltcl.sgml
+++ b/doc/src/sgml/pltcl.sgml
@@ -66,6 +66,7 @@
     directory if Tcl support is specified in the configuration step of
     the installation procedure.  To install <application>PL/Tcl</>
     and/or <application>PL/TclU</> in a particular database, use the
+    <command>CREATE EXTENSION</> command or the
     <command>createlang</command> program, for example
     <literal>createlang pltcl <replaceable>dbname</></literal> or
     <literal>createlang pltclu <replaceable>dbname</></literal>.
diff --git a/doc/src/sgml/ref/create_language.sgml b/doc/src/sgml/ref/create_language.sgml
index c9cb95cae59..13c3baf993c 100644
--- a/doc/src/sgml/ref/create_language.sgml
+++ b/doc/src/sgml/ref/create_language.sgml
@@ -37,6 +37,21 @@ CREATE [ OR REPLACE ] [ TRUSTED ] [ PROCEDURAL ] LANGUAGE <replaceable class="pa
    defined in this new language.
   </para>
 
+  <note>
+   <para>
+    As of <productname>PostgreSQL</productname> 9.1, most procedural
+    languages have been made into <quote>extensions</>, and should
+    therefore be installed with <xref linkend="sql-createextension">
+    not <command>CREATE LANGUAGE</command>.  Direct use of
+    <command>CREATE LANGUAGE</command> should now be confined to
+    extension installation scripts.  If you have a <quote>bare</>
+    language in your database, perhaps as a result of an upgrade,
+    you can convert it to an extension using
+    <literal>CREATE EXTENSION <replaceable>langname</> FROM
+    unpackaged</literal>.
+   </para>
+  </note>
+
   <para>
    <command>CREATE LANGUAGE</command> effectively associates the
    language name with handler function(s) that are responsible for executing
diff --git a/doc/src/sgml/ref/drop_language.sgml b/doc/src/sgml/ref/drop_language.sgml
index 6bf900e2546..21c9e5aced6 100644
--- a/doc/src/sgml/ref/drop_language.sgml
+++ b/doc/src/sgml/ref/drop_language.sgml
@@ -33,6 +33,15 @@ DROP [ PROCEDURAL ] LANGUAGE [ IF EXISTS ] <replaceable class="PARAMETER">name</
    previously registered procedural language.  You must be a superuser
    or the owner of the language to use <command>DROP LANGUAGE</>.
   </para>
+
+  <note>
+   <para>
+    As of <productname>PostgreSQL</productname> 9.1, most procedural
+    languages have been made into <quote>extensions</>, and should
+    therefore be removed with <xref linkend="sql-dropextension">
+    not <command>DROP LANGUAGE</command>.
+   </para>
+  </note>
  </refsect1>
 
  <refsect1>
diff --git a/doc/src/sgml/xplang.sgml b/doc/src/sgml/xplang.sgml
index 0aef3bf4b3d..68220bf6334 100644
--- a/doc/src/sgml/xplang.sgml
+++ b/doc/src/sgml/xplang.sgml
@@ -54,7 +54,7 @@
 
    <para>
     For the languages supplied with the standard distribution, it is
-    only necessary to execute <command>CREATE LANGUAGE</>
+    only necessary to execute <command>CREATE EXTENSION</>
     <replaceable>language_name</> to install the language into the
     current database.  Alternatively, the program <xref
     linkend="app-createlang"> can be used to do this from the shell
@@ -65,8 +65,7 @@
 createlang plperl template1
 </programlisting>
     The manual procedure described below is only recommended for
-    installing custom languages that <command>CREATE LANGUAGE</command>
-    does not know about.
+    installing languages that have not been packaged as extensions.
    </para>
 
    <procedure>
@@ -76,10 +75,10 @@ createlang plperl template1
 
     <para>
      A procedural language is installed in a database in five steps,
-     which must be carried out by a database superuser.  (For languages
-     known to <command>CREATE LANGUAGE</>, the second through fourth steps
-     can be omitted, because they will be carried out automatically
-     if needed.)
+     which must be carried out by a database superuser.  In most cases
+     the required SQL commands should be packaged as the installation script
+     of an <quote>extension</>, so that <command>CREATE EXTENSION</> can be
+     used to execute them.
     </para>
 
     <step performance="required" id="xplang-install-cr1">
@@ -136,14 +135,14 @@ CREATE FUNCTION <replaceable>inline_function_name</replaceable>(internal)
 CREATE FUNCTION <replaceable>validator_function_name</replaceable>(oid)
     RETURNS void
     AS '<replaceable>path-to-shared-object</replaceable>'
-    LANGUAGE C;
+    LANGUAGE C STRICT;
 </synopsis>
      </para>
     </step>
 
     <step performance="required" id="xplang-install-cr5">
      <para>
-      The PL must be declared with the command
+      Finally, the PL must be declared with the command
 <synopsis>
 CREATE <optional>TRUSTED</optional> <optional>PROCEDURAL</optional> LANGUAGE <replaceable>language-name</replaceable>
     HANDLER <replaceable>handler_function_name</replaceable>
@@ -154,7 +153,7 @@ CREATE <optional>TRUSTED</optional> <optional>PROCEDURAL</optional> LANGUAGE <re
       the language does not grant access to data that the user would
       not otherwise have.  Trusted languages are designed for ordinary
       database users (those without superuser privilege) and allows them
-      to safely create of functions and trigger
+      to safely create functions and trigger
       procedures. Since PL functions are executed inside the database
       server, the <literal>TRUSTED</literal> flag should only be given
       for languages that do not allow access to database server
@@ -201,7 +200,7 @@ CREATE FUNCTION plperl_inline_handler(internal) RETURNS void AS
     '$libdir/plperl' LANGUAGE C;
 
 CREATE FUNCTION plperl_validator(oid) RETURNS void AS
-    '$libdir/plperl' LANGUAGE C;
+    '$libdir/plperl' LANGUAGE C STRICT;
 </programlisting>
      </para>