#!/usr/bin/perl -w

use strict;
use warnings;
use Bit::Vector;

my @array;  # contains numbers (1..1000000) ~ 400000 numbers

my $vector = Bit::Vector->new(1000001);
# please replace this bit ---------
map { $vector->Bit_On($_) } @array;
# ---------------------------------
open (IN , "<", "in.txt") or die "$!";
while(<IN>){
    m/^(\d+)/;
    print $_, ', ' if ($vector->bit_test($_));
} 
close IN;