Thanks for your comments. As you may guess, I've barely started with Wx, so I didn't even notice Wx::Dialog yet :-) Now that I've tried it, there seems to be a problem with not creating any top level window within Wx::App::OnInit. I have this:

sub OnInit {
  my $self = shift;
  $$cancel = LoginWindow->new(
    $user,
    $passwd,
    undef,         # Parent window
    -1,            # Window id
    'Login',       # Title
    [200,200],     # position X, Y
    [200,150],     # size X, Y
    wxCAPTION | wxSYSTEM_MENU
  )->ShowModal;
}
[download]

If ShowModal returns true, the app hangs, if it returns false, then I get this error from this code within Wx::App:

  my $ret = Wx::_App::Start($this,$this->can('OnInit'));
  Wx::_croak( 'OnInit must return a true return value' )
    unless $ret || Wx::wxMAC(); # why does OnInit always return 0 on M
+ac?
[download]

In the WxWindows documentation, it says to return a false value from OnInit to exit the application. I don't know why WxPerl would require a true value; it seems like a bug to me. I think I would like to just set $$cancel and then return false from OnInit unconditionally.

Update: Ahh, if I wrap the call to the App constructor in an eval, I don't get the error message, and I can filter for that particular message in $@, but I still think returning false from OnInit should be perfectly valid.