$folder = $entryfolder->get();#get the value from the entry widget
my @chars = split //,$folder;
foreach (@chars){
  if($_ eq "*" || $_ eq '$' || $_ eq "&" || $_ eq "." || $_ eq "?" || $_ eq '\'){
    $dialog = $sw-> Dialog(
    -title=> 'Alert',
    -text => "Special characters appear in the name of your folder.",
    -buttons => [ qw(OK) ])
    ->Show();
  }
}