One of the cool features of PostgreSQL is the privilege for you to write your stored procedures in almost any language you want. Some languages such as SQL, PL/pgSQL, PL/Perl, PL/Python, and PL/Tcl are shipped along with the core of the system. You can also add other languages such as PL/sh, PL/v8, and many more to PostgreSQL to make sure that you always have the language of your choice at hand when you want to write a procedure.

To enable a procedural language, you can call CREATE LANGUAGE.

test=# \h CREATE LANGUAGE
Command:     CREATE LANGUAGE
Description: define a new procedural language
Syntax:
CREATE [ OR REPLACE ] [ PROCEDURAL ] LANGUAGE name
CREATE [ OR REPLACE ] [ TRUSTED ] [ PROCEDURAL ] LANGUAGE name
    HANDLER call_handler [ INLINE inline_handler ] [ VALIDATOR valfunction ]

To enable PL/Perl, just call this command:

CREATE LANGUAGE plperl...