use Math::FFT
my @samples;
{
    local $/=\2048;
    # about 1/5 or 1/10 of a second at 11025 or 22050 sps
    # pick longer samples to be able to see lower frequencies
    binmode;
    @samples = <>;
}
# lets look at about 10 or 20 seconds in
# should check if the sample exists in production code
my $auft = Math::FFT->new([unpack 's*', $samples[100]]);

my $power_spectrum = $auft->spctrm( [window => 'hamm'] );
my $dominant = (sort {$power_spectrum->[$a] <=> $power_spectrum->[$b]} 0..$#power_spectrum)[-1];