my @array_of_objects = (
	{ sex=>'Male', occupation=>'foo' },
	{ sex=>'Female', occupation=>'foo' },
	{ sex=>'Male', occupation=>'bar' },
	{ sex=>'Female', occupation=>'bar' },
	{ sex=>'Female', occupation=>'foo' },
);

my %counts;
$counts{ $_->{sex} }++ for @array_of_objects;

my %grouped;
$grouped{ $_->{sex} }{ $_->{occupation} }++ for @array_of_objects;

use Data::Dumper;
print Dumper( \%counts, \%grouped );

__END__

$VAR1 = { 'Female' => 3, 'Male' => 2 };
$VAR2 = { 'Female' => { 'bar' => 1, 'foo' => 2 },
          'Male' => { 'foo' => 1, 'bar' => 1 } };