sub replace {
    my ($text,$start_index,$end_index) = @_;
    my $old_data = $text->get($start_index,$end_index);
    print "<$old_data>\n";
    $old_data =~ s/cdefg/12345/g;
    $text->delete($start_index,$end_index);
    $text->insert($start_index,$old_data);
    my $old_data = $text->get('3.0',$end_index);
    print "<$old_data>\n";
    return;
}