If Table->clear does it, you can copy Table->clear in your code

BEGIN {
*Tk::Table::clear = \&clear
  unless defined &Tk::Table::clear;
}
sub clear {
    my $self = shift;
    my $rows = $self->cget(-rows);
    my $cols = $self->cget(-columns);
    foreach my $r (1 .. $rows) {
    foreach my $c (1 .. $cols) {
        my $old = $self->get( $r, $c );
        next unless $old;
        $self->LostSlave($old);
        $old->destroy;
    }
    }
    $self->_init;
    $self->QueueLayout(_SlaveSize);
}
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