[perl #78278] [BUG] The optional $_ seems to default to $CALLER::_, not $OUTER::_ in Rakudo

[Matthew Wilson via RT]

new behavior: 

12:18 <diakopter> m: my $b; { my $_ = 5; $b = { .say } }; $_ = 42; $b()
12:18 <camelia> rakudo-moar 61d231: OUTPUT«Potential difficulties:␤    
Redeclaration of symbol $_␤    at 
                /tmp/7gI9FhwrCH:1␤    ------> my $b; { my $_⏏ = 5; $b = { .say 
} }; $_ = 42; $b()␤42␤»