my %merge;
    for my $key (  keys %myhash  )
    {
        push @{ $merge{ join $;, sort @{ $myhash{$key}} } }, $key;
    }

##</code><code>##

#! perl -w
use strict;
use Data::Dumper;

my %d = ( 
    a => [ 'one', 'two' ], 
    b => [ 'one' ], 
    c => ['one', 'two'], 
    d => ['two', 'one'], 
    e => [ 'one', 'two', 'three' ] 
); 

my %merge; 

for my $key ( keys %d ) 
{ 
    push @{ $merge{ join $;, sort @{ $d{$key}} } }, $key; 
} 

print Data::Dumper->Dump( [\%d, \%merge], ['d','merge'] );

__END__

$d = {
       'e' => [
                'one',
                'two',
                'three'
              ],
       'a' => [
                'one',
                'two'
              ],
       'b' => [
                'one'
              ],
       'c' => [
                'one',
                'two'
              ],
       'd' => [
                'two',
                'one'
              ]
     };
$merge = {
           'one' => [
                      'b'
                    ],
           'one‡˜three‡˜two' => [
                                'e'
                              ],
           'one‡˜two' => [
                          'a',
                          'c',
                          'd'
                        ]
         };