CPL is an XML-based language, while sip-cgi is a mechanism for invoking scripts or programs written in any language. sip-cgi is very similar to web cgi scripts.

In its current version, CPL is only invoked when INVITE requests and responses arrive, while sip-cgi can intercept any request.

sip-cgi is designed to be used by SIP, while CPL can probably be used by a number of signaling protocols such as Q.931 or H.323.

CPL and sip-cgi differ in their applicability. CPL is designed for end user service creation. It is intentionally limited in capabilities and is not a general purpose programming language. Its execution on a server is generally very fast. CGI is more powerful - you can do nearly anything. It is programming language independent. It incurs a process-spawning overhead, so its less efficient than CPL. (CPL is usually executed in the same process as the server). As a service provider, I would not want to execute CGI scripts sent to me by end users. However, I would prefer to use CGI to develop my own services.

Note that CGI may be used as the execution environment for a CPL script. (Jonathan Rosenberg)