Note: In the following source code,
replace "∃" with the UTF-8 representation of "∃", and
replace "трщь" with the UTF-8 representation of "трщь".

use strict;
use warnings;

no warnings 'redefine';

for (
   [ "Symbol,  use utf8: " => "use utf8; sub ∃    {}" ],
   [ "Symbol,  no  utf8: " => "no  utf8; sub ∃    {}" ],
   [ "Russian, use utf8: " => "use utf8; sub трщ&#11
+00; {}" ],
   [ "Russian, no  utf8: " => "no  utf8; sub трщ&#11
+00; {}" ],
) {
   print $_->[0], eval "$_->[1]; 1" ? "Success\n" : $@;
}
[download]

outputs

Symbol,  use utf8: Illegal declaration of anonymous subroutine at (eva
+l 1) line 1.
Symbol,  no  utf8: Illegal declaration of anonymous subroutine at (eva
+l 2) line 1.
Russian, use utf8: Success
Russian, no  utf8: Illegal declaration of anonymous subroutine at (eva
+l 4) line 1.
[download]

If the problem is what you say it is, wouldn't use utf8 have no effect on the error?