sub walk(&@) {
   my ($cb, $rez) = @_;
   for my $host ( keys %$rez ) {
   for my $tgt  ( keys %{ $rez->{$host}{tgt} } ) {
   for my $dev  ( keys %{ $rez->{$host}{tgt}{$tgt} } ) {
      $cb->($tgt, $dev, $rez->{$host}{tgt}{$tgt}{$dev});
   }}}
}

walk {
    my ($tgt, $dev, $val) = @_;
    ...
} \%rez;