That's useless. DATA, being the handle used by perl to read the source, is affected by the existing use utf8;.

use if $ARGV[0], "utf8";
printf "%vX\n", scalar(<DATA>);
__DATA__
é
[download]

$ perl a.pl 0
C3.A9.A

$ perl a.pl 1
E9.A
[download]

The OP's problem appears to be a lack of encoding of the output, not a lack of decoding of the input.