PLPerl

PL/Perl is a procedural language for PostgreSQL that enables writing stored procedures, functions, and triggers in the Perl programming language. It is distributed as an extension in PostgreSQL’s contrib modules, available as plperl (trusted) and plperlu (untrusted). When installed, the language handler is loaded into the server and functions are created with a statement such as CREATE FUNCTION ... LANGUAGE plperl or LANGUAGE plperlu.

Programming in PL/Perl runs inside the PostgreSQL backend and can interact with the database through the Server Programming Interface (SPI). A PL/Perl function receives its arguments in the standard Perl array @_, returns a value, and can issue SQL commands via SPI. The language provides access to PostgreSQL data types and supports typical Perl data structures and libraries, making it suitable for text processing, data transformation, and lightweight integration tasks within the database.

Installation and usage typically require Perl to be installed on the database server. The extension is installed from PostgreSQL’s contrib repository and activated with CREATE EXTENSION plperl for the trusted variant or CREATE EXTENSION plperlu for the untrusted variant. Example usage includes defining functions in Perl code blocks and calling them from SQL.

Security considerations distinguish the two variants: plperl runs with restricted privileges suitable for trusted environments, while plperlu allows broader operations, including filesystem access and external program execution, subject to PostgreSQL and OS permissions. Administrators can control which variant is available in a given database or cluster.

PL/Perl is one option among PostgreSQL’s procedural languages and is often chosen for tasks that benefit from Perl’s text processing capabilities or existing Perl modules, while recognizing potential trade-offs in portability, maintenance, and performance compared to native SQL or PL/pgSQL.