The simple solution; replace:

  $dialog->destroy;

With:

  $dialog->Subwidget('Done')->Invoke();

Ok, now for the long explanation...

Your problem lies with the following:

sub getResults {
# ...
  $ltb->bind("<Double-1>", sub { searchGet($dialog, $ltb);});
# ...
}

sub searchGet {
# ...
  $dialog->destroy;
# ...
}
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When you Show() a Tk::DialogBox, it calls $toplevel->waitVariable(...) to create modality (ie, so that it doesn't return until the user has clicked a button). So that the application doesn't freeze while waiting, waitVariable() processes any events normally. Therefore, your bind() handler is actually called while the DialogBox is still waiting for a(n internal) variable to change (ie, a button to be clicked).

When your double-click handler is invoked and calls searchGet(), which then destroys the DialogBox, Tk is still waiting for that variable to change. Tk dutifully continues to wait even after the MainWindow is closed. Incidentally, the DialogBox you destroyed constituted the only way for that variable to actually change. You're pretty much stuck. Instead of bypassing the DialogBox's inner workings, you should've programatically invoked the correct button to submit the dialog choice.

Update: Restructured post to put the simple, practical answer at the top where it should be. :)

bbfu
Black flowers blossom
Fearless on my breath