3 kinds of yadda

[email protected] (Parrot Raiser) Mon, 10 Sep 2018 15:08:52 -0400

Newsgroups	perl.perl6.language
Message-ID	<CACwLAp_mnjGmZ6=tVunSZRxWCezGh1a8D2UYRenAG23Oz2-OHA@mail.gmail.com>

There are 3 kinds of yadda, yadda operator:

!!! dies with a message: Stub code executed
  in block <unit> at yad1 line 2

... dies with an identical message

??? produces the message, but continues operating.

The only difference I can find between !!! and ... is that !!!
produces bizarre behaviour  when run from the command line.
(Bash appears to be interpreting !! as "rerun the previous command",
even when quoted.)

What is supposed to be the difference between !!! and ...?