my $file_count = @ARGV;
foreach my $key1 ( keys %seen ) {
    if ( @{ $seen{$key1} } >= $file_count) {
        print join( "\t", @{$seen{$key1}});
        print "\n\n";
    }
}

##</code><code>##

# At the top of the file
use constant { 
    Key => 0,
    Sum => 1,
    Count => 2, # Remove this if you don't use the total count
    Files => 3  # Should be 2 if Count is not used.
};

##</code><code>##

# In the read loop
$seen{$key1}[Key] //= $key;
$seen{$key1}[Sum] += $value;
$seen{$key1}[Count]++;         # Total count for the number of times this value exists
$seen{$key1}[Files]{$ARGV}++;  # Count in this file


##</code><code>##

use Data::Dumper;
while (<>)
{
  # Your code here
}
print Dumper(\%seen);


##</code><code>##

use YAML;
while (<>)
{
  # Your code here
}
print YAML::Dump(\%seen);