[perl #127906] [REGEX] Array interpolation depends on order of array elements

[Sam S. via RT]

On Wed, 20 Jul 2016 08:32:12 -0700, c...@zoffix.com wrote:
> I was able to golf it a bit further (still present in Rakudo 58dc8c).
> Removing >> or changing first-match || to longest-match | no longer
> shows the bug:
> 
> m: "bc" ~~ /||@(<b bc>) >>/ or say "Failed"
> rakudo-moar 58dc8c: OUTPUT«Failed␤»

Still present in:

    This is Rakudo version 2017.09-227-g8ff76b596
    built on MoarVM version 2017.09.1-575-gd4e230a6
    implementing Perl 6.c.

And it's not specific to `>>`. Even simpler test-case:

    ➜  say "abc" ~~ /[ a || ab ] c/;  # ｢abc｣
    ➜  say "abc" ~~ /||@(<a ab>) c/;  # Nil

It looks like it simply refuses to backtrack into `||@`.