As the man page for tclvars mentions, one can examine TBC by generation of Tcl with TCL_COMPILE_DEBUG, followed by execution in a run-time context with at least one of tcl_traceCompile and tcl_traceExec non-zero.
DKF provides a different formula, relying on --enable-symbols=compile, in this [L1 ] comp.lang.tcl posting.
Tcl 8.5 now has the tcl::unsupported::disassemble command.