my $i;
for ($i = 0; $i < @un; $i++) 
{
    my $username = $un[$i];
    my @username = @$username;
    $sth->execute($username[0]) or die $dbh->errstr;
    $uid = $sth->fetchrow_array;
    unless ($uid)
    {
        warn "User $username[0] missing.\n";
        # remove element from array
        splice (@un, $i, 1);
        next;
    }
    $info{$uid} = $role;
}