my %h1 = map { ( $_ => 1 ) } qw( a b c d e f g h );
my %h2 = map { ( $_ => 1 ) } qw(   b c d e f g h i  );
my %h3 = map { ( $_ => 1 ) } qw(     c d e f g h i j );
my %h4 = map { ( $_ => 1 ) } qw(       d e f g h i j k );

my %summed = add_hashes(
	\%h1,
	\%h2,
	\%h3,
	\%h4,
);

use Data::Dumper;
$Data::Dumper::Sortkeys=1;
print Dumper \%summed;