[perl #131856] [@LARRY] Junctions don't junct when routine has a slurpy, leading to inconsistent behaviour with core routines

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# New Ticket Created by  Zoffix Znet 
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Originally taken from: 
https://stackoverflow.com/questions/45527881/why-does-and-affect-perl-6-junctions-differently

For example, there's a difference between output of using `+` and using `~` 
with a Junction. With `+` you get a junction back, while `~` slurps and just 
.Strs (which .perls) the Junction:

    <Zoffix__> put any( 1, 3, 7 ) + 1;
    <Zoffix__> m: put any( 1, 3, 7 ) + 1;
    <camelia> rakudo-moar a91ad2: OUTPUT: «any(2, 4, 8)␤»
    <Zoffix__> m: put any( <h H> ) ~ 'amadryas';
    <camelia> rakudo-moar a91ad2: OUTPUT: «any("h", "H")amadryas␤»

The reason is the `~` has a slurpy candidate, while `+` doesn't:

Junction as just an arg:
    <Zoffix__> m: sub foo (+@a) { @a.join: '|' }; say foo <h H>.any, 'amadryas' 
    <camelia> rakudo-moar a91ad2: OUTPUT: «any("h", "H")|amadryas␤»
    <Zoffix__> m: sub foo (*@a) { @a.join: '|' }; say foo <h H>.any, 'amadryas' 
    <camelia> rakudo-moar a91ad2: OUTPUT: «any("h", "H")|amadryas␤»

Junctioned call:
    <Zoffix__> m: sub foo ($a, $b) { ($a, $b).join: '|' }; say foo <h H>.any, 
'amadryas' 
    <camelia> rakudo-moar a91ad2: OUTPUT: «any(h|amadryas, H|amadryas)␤»

There are two question:
    1) Is it possible to make slurpies junct, same as non-Mu scalar candidates?
    2) If not, what do we do to make interface consistent; so that all the ops 
do the same thing?