use Tk;
use POE;

POE::Session->create(
  inline_states => {
    _start   => \&handle_start,
    ev_count => \&handle_count,
    ev_clear => \&handle_clear,
  }
);

POE::Kernel->run();
exit 0;

sub handle_start {
  $poe_main_window->Label(
    -text => "Counter"
  )->pack;

  $_[HEAP]->{counter_widget} =
    $poe_main_window->Label(
      -textvariable => \$_[HEAP]->{counter}
    )->pack;

  $poe_main_window->Button (
    -text => "Clear",
    -command => $_[SESSION]->postback("ev_clear")
  )->pack;

  $_[KERNEL]->yield("ev_count");
}

sub handle_count {
  $_[HEAP]->{counter}++;
  $_[KERNEL]->yield("ev_count");
}

sub handle_clear {
  $_[HEAP]->{counter} = 0;
}