On RH6.1 and 6.2 the 'fconfigure' command does not work. So Tcl/Tk programs using the serial port do not work. You can run my program 'tkusr' to check the problem. Some users have reported that running and re-compiling tcl/tk 8.0.x (from a RH5.2) or tcl/tk 8.3.x, on a RH6.2 fixed the problem.
tcktk-8.3.[12] are available in Red Hat 7.0 (and RawHide). The problem does not seem impirtant enough to issue an errata for Red Hat 6.x, use one of the suggested work arounds (i.e. recompile from a src.rpm).
Anyway, I does not matter, since It works on Debian :-)))))) (I'm astounded by the lack of professionalism of so called professionals)