#!/usr/local/bin/perl  
 
use strict; 
 
my $max = 0;

sub readfile { 
  my $fn=shift; 
  my @ar; 
 
  open IN,"<$fn" || die "Couldn't open '$fn': $!"; 
  ## snarf the header 
  scalar <IN>; 
  ## read the rest 
  while (<IN>) { 
    chomp; 
    push @ar,$_; 
    $max = $_ if $_ > $max;
  } 
  close IN; 

  @ar; 
} 
 

## load the files into arrays 
my @a=readfile 'f1.lst'; 
my @b=readfile 'f2.lst'; 
my @c=readfile 'f3.lst'; 
 
## iterate until all arrays are empty 
for (my $i = 0; $i <= $max; $i++)
{
  next unless $a[0] == $i || $b[0] == $i ||$c[0] == $i;
 
  ## print them out (if they match) 
  printf "%5s", $a[0]==$i ? scalar shift @a : undef; 
  print " | "; 
  printf "%5s", $b[0]==$i ? scalar shift @b : undef; 
  print " | "; 
  printf "%5s", $c[0]==$i ? scalar shift @c : undef; 
 
  print "\n"; 
}