foreach my $k ( keys %{HoH} ) 
{
    unless ( $HoH{$k} and values %{$HoH{$k}} ) 
    {
       delete $HoH{$k};
    }
}

##</code><code>##

my %HoHCopy;
foreach my $k ( keys %HoH ) 
{
    if ( $HoH{$k} and values %{$HoH{$k}} ) 
    {
       $HoHCopy{$k} = $HoH{$k};
    }
}

##</code><code>##

my %HoHCopy = map
  { $_ => $HoH{$k} }
  grep {
    $HoH{$_} and values %{$HoH{$_}}
  } ( keys %HoH );

# or 

my %HoHCopy = map
  {
    ($HoH{$_} and values %{$HoH{$_}})
    ? ($_ => $HoH{$k})
    : ()
  } ( keys %HoH );