use strict;
use warnings;

my ($file1, $file2) = @ARGV;

my $maxL = 40; # max name length
my $ids = 10000000;  # last id
my $bin="\0" x ($maxL * $ids) ;

# Create the index
open my $fh1, "<", $file1 or die $!; 
while (<$fh1>){
	chomp;
	my ($id,$name) = split /\s+/;
	substr($bin, $id*$maxL, $maxL, pack ("A$maxL",$name));
}
close $fh1;

# Search $ids from file 2
open my $fh2, "<", $file2 or die $!;
while (<$fh2>){
	chomp;
	my $binval = substr ($bin,$_*$maxL,$maxL);
	my $valback = unpack ("A$maxL",$binval);
	print "$_ => $valback\n";
}
close $fh2;