Here is a performance-improved version of perlcapt's solution - this one includes a response to your last query. 
#!/usr/bin/perl -w
use strict;
use warnings;

my %hash = (
          'a' => {
                   'x' => 40,
                   'z' => 102
                 },
          'b' => {
                   'z' => 100,
                   'x' => 10,
                   'y' => 20
                 },
          'c' => {
                   'x' => 50
                 },
          'd' => {
                   'z' => 101,
                   'y' => 30
                 }
        );

sub stats {
    my ($hhp, $SearchKey, $SearchVal) = @_;
    my %counters; # a counter hash of which keys are used at level two
    my $SearchCount;

    foreach my $key1 (keys %$hhp) {
        my @cList = keys %{$hhp->{$key1}};
        ++$counters{join('+',sort @cList)};
        ++$SearchCount if exists $hhp->{$key1}->{$SearchKey} 
                         and $hhp->{$key1}->{$SearchKey} == $SearchVal
+;
    }
    return $SearchCount, %counters;
}

#### main
my ($SearchCount, %result) = stats(\%hash,'z',101);
foreach my $key (sort keys %result){
    print "$key \t$result{$key}\n";
}
print "Count of z==101 is $SearchCount\n";
__END__
## OUTPUT ##
x       1
x+y+z   1
x+z     1
y+z     1
Count of z==101 is 1

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    Earth first! (We'll rob the other planets later)

In reply to Re: Counting hash of hashes elements by NetWallah
in thread Counting hash of hashes elements by albert

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