#!/usr/bin/perl -w

use strict; use warnings; 

my $ar=[
       {sex=>'m',occupation=>'programmer',state=>'CA'},
       {sex=>'m',occupation=>'blah1',state=>'CA'},
       {sex=>'m',occupation=>'blah1',state=>'NY'},
       {sex=>'m',occupation=>'blah2',state=>'NY'},
       {sex=>'f',occupation=>'blah1',state=>'NY'},
       {sex=>'f',occupation=>'blah2',state=>'NJ'},
       ];

printer(counter($ar,['sex'])); 
printer(counter($ar,['sex','state'])); 
printer(counter($ar,['sex','occupation'])); 
printer(counter($ar,[])); 
exit; 

sub printer{ 
  use Data::Dumper;
  my $ref=shift; 

  local $Data::Dumper::Deepcopy=1;
  local $Data::Dumper::Purity=1;
  local $Data::Dumper::Sortkeys=1;
  local $Data::Dumper::Indent=2; 

  print Dumper($ref)."\n";
} # printer 

sub counter { 
  my $arin=shift; 
  my $arparts=shift; 
  my $res={}; 
  my $size1=scalar(@$arparts)-1; 
  return  $res unless ($size1 >=0); 
  my $size2=$size1-1; 

  for my $hash (@$arin){ 
  my @parts=(); 
  for my $key (@$arparts){ 
    my $val=$hash->{$key};
    if (!defined ($val)) {$val='.'}
    push @parts,$val;
    } 

  my $reshead=$res; 
  for my $n (0..$size2) { 
    my $val=$parts[$n]; 
    unless ($reshead->{$val}) {$reshead->{$val}={};} 
    $reshead=$reshead->{$val};
    } 
  $reshead->{$parts[$size1]}++;
  } # hash 

return $res; 
}  # counter