#!/usr/bin/perl
open FH1, "F1.txt";
open FH2, "F2.txt";
my @f1= <FH1>;
my @f2= <FH2>;
for my $x(0..4)
{
 for each($f1[$x1] eq $f2[$x2])
  {
   print $f1[$x];
   }
}
close(FH1);
close(FH2);
exit;

##</code><code>##

F1.txt
name   value
n1       001
n2       002
n3       003
n4       004

F2.txt
name     value
n5       005
n2       002
n3       003
n8       008