This is a loadable extension to Tcl providing commands for data conversion, message digests, zlib based compression, error-correction, channel-based manipulation of binary data. Trf extends the language at the C-level with so-called ``transformer''-procedures. With the help of some patches (*) to the core the package is able to intercept all read/write operations on designated channels, thus giving it the ability to transform the buffer contents as desired. This allows things like transparent encryption, compression, charset recoding, etc. Build upon this framework (and as proof of concept) a collection of tcl-level commands was implemented. WWW: http://www.oche.de/~akupries/soft/trf/