Use gridForget() instead. You'll lose your configuration options, but it seems to work.

And some sample code, just because:

#!/usr/bin/winperl
use warnings;
use strict;

use Tk;

my $mw = MainWindow->new();

$mw->Label(-text => 'Do it')->grid();
my $btn;
$btn = $mw->Button(
  -text => 'Click me',
  -command => sub { $btn->gridForget() },
)->grid();

MainLoop;
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bbfu
Black flowers blossom
Fearless on my breath