Works for me:

$ cat /tmp/p
my $HoHref = { a => { p => 1 }, b => { q => 1 } };
use Data::Dumper;
print Dumper $HoHref;
delete $HoHref->{a};
print Dumper $HoHref;
$
$ perl /tmp/p
$VAR1 = {
          'a' => {
                   'p' => 1
                 },
          'b' => {
                   'q' => 1
                 }
        };
$VAR1 = {
          'b' => {
                   'q' => 1
                 }
        };
[download]

You'll need to give more details, such as a small (but complete) sample script, for us to help you further.

Dave.