tkDerm is a Tcl/Tk script consisting of over fifteen thousand lines. To structure such a large program, tkDerm has a short main program named tkderm.tcl and a library of support scripts. The Tcl package facility provide a convenient way for organizing a large program by this strategy. By using the package system and the namespace facility, which is another Tcl invention to support a large scale application development by providing a way to avoid conflicts between procedures and global variables used in different packages, tkDerm is divided into over twenty modules. Furthermore, tkDerm provide a facility to make it easy to add your own package by yourself.
This chapter describes how to add your own functions to tkDerm with the package facility.