use Tie::File;
use Fcntl 'O_RDONLY';
my @array;
my $filename = '/etc/passwd';
tie @array, 'Tie::File', $filename, mode=>O_RDONLY or die;

open NUMS, "line_num_file" or die;
my @line_nums = map { s/\s+$//s; $_ } <NUMS>;
close NUMS;

my @lines = @array[ @line_numes ];