use Encode qw(is_utf8);
# check if $str is UTF8 and contains bad UTF8.
print "bad UTF8\n" 
    if is_utf8($str) and not is_utf8($str, 1);

##</code><code>##

iconv -c --from UTF-8 --to UTF-8

##</code><code>##

use Text::Iconv;
my $conv = Text::Iconv->new("utf8", "utf8");
$str = $conv->convert($str);