Any Code[+] scalar sub truth $b->($a)
Hash Hash hash keys identical [sort keys %$a]~~[sort keys %$b]
- Hash Array hash slice existence grep {exists $a->{$_}} @$b
+ Hash Array hash slice existence @$b == grep {exists $a->{$_}} @$b
Hash Regex hash key grep grep /$b/, keys %$a
Hash Any hash entry existence exists $a->{$b}