[perl #127165] [FEATURE] make :%hash a pair constructor

[via RT]

# New Ticket Created by  Tobias Leich 
# Please include the string:  [perl #127165]
# in the subject line of all future correspondence about this issue. 
# <URL: https://rt.perl.org/Ticket/Display.html?id=127165 >


For a while we can create Pairs from named captures of match variables:
m: my %hash = key => 42; say (:$<key>)
rakudo-moar ac4f9f: OUTPUT«key => Nil␤»

Sadly, this does not even parse:
m: my %hash = key => 42; say (:$/<key>)
rakudo-moar ac4f9f: OUTPUT«===SORRY!=== Error while compiling 
/tmp/3GMq24eXRj␤Bogus statement␤at /tmp/3GMq24eXRj:1␤------> my %hash = 
key => 42; say (:$⏏/<key>)␤    expecting any of:␤        colon pair␤»

Nor does this create a Pair:
m: my %hash = key => 42; say (:%hash<key>)
rakudo-moar ac4f9f: OUTPUT«(Mu)␤»

So I vote for all shown statements to create a Pair of key => Nil or key 
=> Any respectively.

Funnily, Arrays behave differently when used with colonpair syntax:
m: my @array = 42, 43; say (:@array[0])
rakudo-moar ac4f9f: OUTPUT«array => [42 43]␤»

Which is also wrong, IMO.
This case should either produce 0 => 42, or array => 42.
If we go for the latter then the shown Hashes should also be treated as 
subscripts, and produce hash => 42, if the variable is not anonymous 
like in $/<key> or $<key>.
This would allow %hash<key foo>, but then again $<key foo> and $/<key 
foo> need to parsefail.