...
    my( avg, $stddev ) = avgNstddev( $bigStruct->{something}{somethingelse} ); ## hash expression yields an array ref.
...

##</code><code>##

...
    my $stats = Stats:Mod->new;
    $stats->add( $_ ) for @{ $bigStruct->{$something}{$somethingelse} };
    my $avg = $stats->avg;
    my $stddev = $stats->stddev;
    $stats->empty;
...

##</code><code>##

for my $something ( keys %bigstruct ) {
    for my $somethingelse ( keys %{ $bigstruct->{ $something } } ) {
         ...
    }
}

##</code><code>##

my $stats = Stats::Module->new( $bigstruct->{ $something }{ $somethingelse } );
my( $avg = ( $stats->average, $stats->stddev );
$stats->done;