Thanks to Bastian Friedrich, the development version of OpenSER includes now a programming interface for Perl. You can build your own extensions as Perl scripts and embed the execution in the OpenSER configuration file. You can have access to OpenSER's functions and structures from Perl applications, the execution's results being returned back and made visible to OpenSER config file.

For those familiar with Asterisk, this is similar to AGI interface. From a Perl application, you can check and reset flags, rewrite URI, play with branches and pseudo-variables, access SIP headers and other parts of SIP requests, plus many other operations, see the readme file of the new Perl module:

 http://www.openser.org/docs/modules/1.2.x/perl.html

Author's announcement on mailing lists:

 http://openser.org/pipermail/users/2006-December/008139.html