#!/usr/bin/perl
use strict;
use warnings;

my $file_1 = $ARGV[0] || 'file1.txt';
my $file_2 = $ARGV[1] || 'file2.txt';

open (FILE1, '<', $file_1) or die "Unable to open $file_1 for reading : $!";
open (FILE2, '<', $file_2) or die "Unable to open $file_2 for reading : $!";
my %offset = ( _pos => 0 );

while ( <FILE1> ) {
    chomp;
    if ( defined $offset{ $_ } ) {
        seek FILE2, $offset{ $_ }, 0;
        print scalar <FILE2>;
        next;
    }
    else {
        seek FILE2, $offset{_pos}, 0;
        my $pos = tell FILE2;
        while ( my $line = <FILE2> ) {
            my ($col1) = $line =~ /^(\d+)/;
            $offset{ $col1 } = $pos;
            $pos = tell FILE2;
            if ( $col1 eq $_ ) {
                print $line;
                $offset{_pos} = $pos;
                last;
            }
        }
    }
}