Yes, do-while is a far worse problem, which is why we changed it to loop-while in Perl 6, and redefined do-block to make it the once-through loop (which conveniently makes it illegal to put a while on it).

I would also submit that the fallthrough of C switches falls into the category of bugs waiting to happen. Fallthrough is approximately the worst way to implement an "or". So that's not how Perl 6 will do it.

Another control flow fixup is to unify loop variables with closure parameters, so there's no longer any weird implicit blocking of special-purpose my variables.

Unifying switches with exception handlers will also prevent a bunch of "roll-your-own" control flow bugs in Perl 6.

If you count OO dispatch as a form of control flow (and I do), the roll-your-own OO support in Perl 5 also contributed to various forms of bugginess. One might go as far as to say that most of the fixups in Perl 6 consist of choosing better defaults (without making them mandatory).