my %lines_of_interest = map { $_ => 1 } 6, 1003, 2965;

open my $fh, '<', $file_name
   or die("Unable to open file \"$file_name\": $!\n");

my $num_lines = keys %lines_of_interest;

while (<$fh>) {
   if ($lines_of_interest{$.}) {
      print;
      last unless --$num_lines;
   }   
}