sub remove_element {
	my @all = $listbox->get(0, 'end');
	my @selected_no = $listbox->curselection();
	my @selected_name;
	my $index = 0;
	foreach(@selected_no){
		push(@selected_name, $listbox->get($_));
	}
	foreach(@selected_name){
		$listbox->delete(
                       get_element_index(\@all, $selected_name[$index]));
		$index++;
	}
}

sub get_element_index {
	my ($arr_reference, $ele) = @_;
	my @arr = @{$arr_reference};
	my $index = 0;
	foreach(@arr){
		if($_ eq $ele){
			return $index;
		}
		$index++;
	}
}