File Extension PL File Format Source code file (Perl) PL stands for Source code file (Perl). This was last updated in March 2012 By Margaret Rouse Browse File Extensions Alphabetically: A B C D E F G H I J K L M N O P Q R S T U V W X Y Z # Ask a Question. Find an Answer. Ask your peers a question about this file extension. Ask a Question WITH clause not working. Managing VMware Infrastructure 3 (VI3) from OS X (10.5.1 Leopard) Chapter 3 -- Databases with Perl -- of 'Beginning Perl Web Development'