Hmm... let's see...

my %temphash;
while (($key,\@val) = each %myhash) {
   $temphash{join sort @val} = $key;
}
undef %myhash;
while (($key,$val) = each %temphash) {
   $myhash{$val} = split $key;
}
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Note: This is untested and will likely go through a couple of Updates.

LAI