Weird rakudo error tied to a code block.md

Here's an interesting bug from Rakudo, that I ran into today. Take this code block:

my $item-type;
$item-type = do given $ii {
  when .key ~~ / ^ '-' /      { 'GTK::SeparatorMenuItem'  }

  # !!! #
  when .value<toggled>:exists |
       .value<check>:exists   |
       .value<toggle>:exists  { 'GTK::CheckMenuItem'      }
  # !!! #

  default                     { 'GTK::MenuItem'           }
}

Looks innocent enough! However when I tried to compile the module that contained this, I got the following error:

===SORRY!===
MVMArray: Index out of bounds

I know for sure it is tied to the when statement between the "# !!! #" comments, but I'm not sure why. I will probably have to re-write this into something else, though.

Just thought I should share.