evalable6

query

say grep { ++$_; True }, 1, 2, 3;

result

(exit code 1) 
Cannot resolve caller prefix:<++>(Int); the following candidates
match the type but require mutable arguments:
    (Mu:D $a is rw)
    (Int:D $a is rw)

The following do not match for other reasons:
    (Bool $a is rw)
    (Mu:U $a is rw)
    (Num:D $a is rw)
    (Num:U $a is rw)
    (int $a is rw)
    (num $a is rw --> num)
  in block <unit> at /tmp/urJYNEJ36e line 1