Writing a Tcl Extension in Only Seven Years

Expect is a tool for automating interactive applications. Expect was constructed using Tcl, a language library designed to be embedded into applications. This paper describes experiences with Expect and Tcl over a seven year period. These experiences may help other extension designers as well as the Tcl developers or developers of any other extension language see some of the challenges that a single extension had to deal with while evolving at the same time as Tcl. Tcl and Expect users may also use these 'war stories' to gain insight into why Expect works and looks the way it does today.