#!/usr/bin/perl
use strict;
use warnings;
use utf8 ();

sub check_flag{
    my $str = shift;
    print qq("$str" ), utf8::is_utf8($str) ? 'is' : 'IS NOT', " flagged.\n";
}

{
    use utf8;
    check_flag("dankogai");
    check_flag("小飼弾");
    check_flag("dankogai" . "小飼弾");
    check_flag("小飼弾" . "dankogai");
}
{
    check_flag("dankogai");
    check_flag("小飼弾");
    check_flag("dankogai" . "小飼弾");
    check_flag("小飼弾" . "dankogai");
}