You can create a new Toplevel, populate it, and tell it to destroy itself after a time passes. For example (untested):

my $box = $mw->Toplevel;
my $message = $box->ROText->pack;
$message->insert(end => "Hey there!  Gotta go!");
$box->after(3000, sub { shift->destroy });
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Yup, that's what I thought! Thanks. :-) This was my other option but thought there was possibly a "message box" way of doing it.

Dean
The Funkster of Mirth
Programming these days takes more than a lone avenger with a compiler. - sam
RFC1149: A Standard for the Transmission of IP Datagrams on Avian Carriers

However this is not something people usually do in GUI design.

It is about what amount of attention you want to draw from the user. If you don't need that much, most likely you really don't need a popup; if you really need that much attention, the right way is to let people click (this is not about to distract people, but to CONFIRM that the user noticed the popup.)

#!/usr/bin/perl
use Tk;
use strict;
my $text = 'Hello World..... How\'s this for fun!!    ';
my $mw = tkinit;
$mw->geometry('+20+20');
$mw->overrideredirect(1);
my $label = $mw->Label(
 -textvariable=>\$text,
  -font=>'courier',
   -bg=>'green',
    -bd=>4,
     -relief=>'ridge'
      )->pack(-fill=>'both');
      $label->bind('<ButtonRelease>',sub{$mw->destroy});
      $mw->repeat(60,[sub{$text=~s/(.)(.*)/$2$1/;}]);
      $mw-> after(5000, [sub{Tk::exit}]); # autoclose in 5000 milisecs
+  
      MainLoop;
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