As you point out, when a MainWindow invents a font, that font is available to all its children. But when I moved the fontCreate lines into the Toplevel window that was containing the Help button, I got the effect I wanted for the Help button but now that Toplevel (a child of the MainWindow) would not reinvoke because its redefinition of fonts would cause the same error.

Moving the definition of the fonts all the way back into the first MainWindow solves the problem since the MainWindow is only invoked once, upon initialization of the program. But this need to create a "global" font for some button a few Toplevels down doesn't feel "right"....

It sounds like you may be allocating this Toplevel each time you want to display it. You might consider allocating the Toplevel once and then mapping/unmapping it as needed. The relevant methods are withdraw and deiconify (see perldoc Tk::Wm), and raise (see perldoc Tk::Widget).

Here is an example from page 233 of Mastering Perl/Tk:

use Tk;
$mw = MainWindow->new;
$mw->title("MainWindow");
$mw->Button(-text => "Toplevel", -command => \&do_Toplevel)->pack();

MainLoop;
sub do_Toplevel {
  if (! Exists($tl)) {
    $tl = $mw->Toplevel();
    $tl->title("Toplevel");
    $tl->Button(-text => "Close",
                -command => sub { $tl->withdraw })->pack;
  } else {
    $tl->deiconify();
    $tl->raise();
  }
}
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This would allow you to invoke fontCreate in the same scope as the widget in which the font is intended to be used. The font definition would still be visible to all children of the MainWindow, but you'd have the illusion of scope and maintenance would be a bit easier.

I've added links to several Perl/Tk-related resources to my home node (with more to come as I find time). Have a look around and you'll probably find a lot of useful information that you didn't know existed.

conv