#!/usr/bin/perl

use warnings;
use strict;

my %hoh = (
    "A1" => { "bl" => 0, "ff" => 4, "gg" => 3 },
    "A2" => { "cc" => 5, "dd" => 4, "ee" => 9 },
    "B1" => { "og" => 0, "wo" => 4, "ee" => 3 },
    "B2" => { "oo" => 5, "pp" => 4, "zz" => 9 }
);

# The names of the hashes to print
my @keys_to_sort = sort keys %hoh;

# As long we still have hashes to print
while ( @keys_to_sort ) {
    # Extract hashes to use in current row
    # Smarter way to get the first part of the hash name?
    my $last = substr $keys_to_sort[0], 0, 1;
    my @keys_to_use;
    for ( my $i = 0; $i < @keys_to_sort; $i++ ) {
        if ( $keys_to_sort[$i] =~ /^$last/ ) {
            push @keys_to_use, splice( @keys_to_sort, $i, 1 );
            $i--;
        }
    }

    print "\n", join( "\t", @keys_to_use ), "\n";
    # Print key number $i of every hash in the array
    # Exchange keys %... with maximum number of keys in @keys_to_use
    for ( my $i = 0; $i < keys %{$hoh{$keys_to_use[0]}}; $i++ ) {
        # Print hashes - This relies on all hashes having
        # the same number of keys
        print join( "\t", map {
            my @keys_of_hash = sort keys %{$hoh{$_}};
            $keys_of_hash[$i] . "=>" . $hoh{$_}{$keys_of_hash[$i]};
        } @keys_to_use ), "\n";
    }
}