On 10/27/2010 02:16 AM, dotnetdub wrote: The best place to learn about types of variables and variable-related syntax and behaviour in general is the core cookbook: http://www.kamailio.org/dokuwiki/doku.php/core-cookbook:3.1.x This also describes many matching operations, operators for prepending, etc. More sophisticated string operations, such as selection of substrings, regular expression matching, component extraction, splitting into tokens by a delimeter, etc. are known as "transformations." They can be applied to most variables, and an examination of them is found here: http://www.kamailio.org/dokuwiki/doku.php/transformations:3.1.x If the question is more about which variables are defined/exposed in certain situations, the pseudovariables doc is most appropriate: http://www.kamailio.org/dokuwiki/doku.php/pseudovariables:3.1.x -- Alex -- Alex Balashov - Principal Evariste Systems LLC 1170 Peachtree Street 12th Floor, Suite 1200 Atlanta, GA 30309 Tel: +1-678-954-0670 Fax: +1-404-961-1892 Web: http://www.evaristesys.com/