To be awfully pedantic the .pl suffix was traditionally used to denote a Perl library prior to the introduction of modules with Perl 5. Some examples (such as ftp.pl) can still be found in the lib directory of a Perl installation - these remain for the support of old code and are not intended to be used in new programs. It might be worth introducing .ph files as well at this point, which are library files derived (using the h2ph utility) from the system's C header files - these are largely obsoleted by the use of XS and there are now no modules (AFAIK) that require their use.

/J\