[perl #132140] Behaviour of bang-bang

[via RT]

# New Ticket Created by  Philippe 'BooK' Bruhat 
# Please include the string:  [perl #132140]
# in the subject line of all future correspondence about this issue. 
# <URL: https://rt.perl.org/Ticket/Display.html?id=132140 >


Experimenting with !! showed this:

    $ perl6 -v
    This is Rakudo version 2017.08-160-g7791dd47d built on MoarVM version 
2017.08.1-171-gcf95892e
    implementing Perl 6.c.

    $ perl6 -e 'say !""'
    True

    $ perl6 -e 'say ! ""'
    True

    $ perl6 -e 'say !!""'
    False

    $ perl6 -e 'say ! !""'
    False

    $ perl6 -e 'say ! ! ""'
    False

    $ perl6 -e 'say !!""'
    False

    $ perl6 -e 'say !! ""'
    Non ast passed to WANTED: NQPMu
    ===SORRY!=== Error while compiling -e
    Two terms in a row
    at -e:1
    ------> say !!⏏ ""
        expecting any of:
            infix
            infix stopper
            postfix
            statement end
            statement modifier
            statement modifier loop

    $ perl6 -e 'say !!'
    ===SORRY!=== Error while compiling -e
    Prefix ! requires an argument, but no valid term found
    at -e:1
    ------> say !!⏏<EOL>
        expecting any of:
            prefix

    $ perl6 -e '!! while 1'
    ===SORRY!===
    Cannot find method 'okifnil' on object of type NQPMu

    $ perl6 -e '! while 1'
    ===SORRY!=== Error while compiling -e
    Undeclared routine:
        while used at line 1