[perl #123777] [BUG] List assignment in a BEGIN block causes a crash at runtime

[Christian Bartolomaeus via RT]

This works on the 'glr' branch:

$ perl6-m -e 'my @a; BEGIN { @a = 42; }; say @a;'
[42]

The test in S04-phasers/begin.t was unfudged with commit 
https://github.com/perl6/roast/commit/b8a19c981c. I'm closing this ticket as 
'resolved'.