warn PerlIO::get_layers($handle{$file});

##</code><code>##

my @l = grep /utf-?8/, PerlIO::get_layers($handle{$file});
warn @l / 2;

##</code><code>##

        binmode $fh, ':raw:encoding(UTF-8)';

##</code><code>##

          Rate   close noclose
close   2137/s      --    -28%
noclose 2951/s     38%      --