PostgreSQL is an advanced object-relational database management system
that supports an extended subset of the SQL standard, including
transactions, foreign keys, subqueries, triggers, and user-defined
types and functions.

This package contains the PL/Tcl, PL/Perl, and PL/Python procedural
languages for PostgreSQL. With these modules one can use Perl, Python,
and Tcl to write stored procedures, functions, and triggers.

PostgreSQL also offers the built-in procedural language PL/SQL which is
included in the postgresql-server package.