Tcl extension providing "transformer" commands

Trf is an extension library to the script language tcl. It provides
transformer procedures which change the flow of bytes through a channel
in arbitrary ways. The underlying functionality in the core is that of
stacked channels which allows code outside of the core to intercept all
actions (read/write) on a channel.

Among the applications of the above provided here are compression,
charset recording, error correction, and hash generation.