I think what you are looking for is waitVisibility. Try the script below, with the sleep statement in the different locations. You should see the way to go. Don't forget, that in your long-process without user interaction, you must include frequent $mw->update to update whatever display widgets you have.

#!/usr/bin/perl
use warnings;
use strict;
use Tk;

my $mw = tkinit;

#for(1..3){sleep 1}; 

#to wait until a $widget is visible, use waitVisibility: 
$mw->waitVisibility;

for(1..3){sleep 1};

MainLoop;
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