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

my $filecount = 25;
my %count = ();
my @files = map { "File $_.txt" }(1..$filecount);
for my $i (0..$#files){
  open IN,'<',$files[$i] or die "Could not open $files[$i] : $!";
  while (<IN>){
    chomp;
    $count{$_}[$i] += 1;
  }
  close IN;
}

my @result=();
print join "\t",'ID    Name',@files,"\n";

for my $key (sort keys %count){
  my @all = ();
  for my $i (0..$#files){
    if (defined $count{$key}[$i]){
      $all[$i] = $count{$key}[$i];
    } else {
      $all[$i] = 0;
    }
  }  
  print join "\t",$key,@all,"\n"; # debug
  
  # skip if any are zero
  next if grep( $_==0, @all );
  
  push @result,$key;
}
print "\nCommon to all\n";
print "$_\n", for @result;