TclBin , by Laurent Demailly, is an extension of Tcl to allow direct access and manipulation of binary data and structures from Tcl. TclBin predates [binary], which was introduced in Tcl 8.0
There was once a mailing list at mail.box.eu.org
TclBin allows access to binary data from Tcl, including a paradigm for pointers, structures, etc. Latest version can be built as a Tcl 7.6 dynamically loadable extension. A sample geturl script is included.
While this version compiles and passes all tests under Tcl 8, it doesn't take advantage of the new Tcl objects.