Hypothetically, if __enter__ could be a generator, with the with body running for each yielded value, that would give us the power to implement class Loop: def __enter__(self): self._do_continue = ...
If by TCL you mean Ousterhout's Tcl, nope. break does not take an argument and nor does continue. Supplying one gives an error, at least in Tcl 8.6.11.