Are you running under mod_perl?

I cannot replicate under cli :)

#!/usr/bin/perl -T
use strict;
use warnings;
use CGI;
use CGI::Carp qw ( fatalsToBrowser );
use Data::Dump qw/ pp /;
my $bom = "bom=\xEF\xBB\xBF";
my $junk = "junk=\xC3\x2E";

my $fun = sub {
    my $q = CGI->new( "$bom;$junk");
    my $qbom = $q->param('bom');
    my $qjunk = $q->param('junk');
    $q->charset('UTF-8');
    print $q->header('text/plain'), join "\n", pp($bom,$qbom),$qbom, p
+p($junk,$qjunk),$qjunk, "\n";
};

$fun->();
local $CGI::PARAM_UTF8 = $CGI::PARAM_UTF8 = 1;
binmode STDOUT, ':encoding(UTF-8)';
$fun->();
__END__
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Also that  [CLOSED] stuff shouldn't have [] you should <p><b>update:</b> solved it , it was ...