use warnings;
use strict;

my %HoA = (
           A => [2.34, 4.12, 5.32],
           B => [1.42, 8.15],
           C => [8.42, 0.23, 0.45, 6.43],
          );

foreach my $key (keys %HoA) {
    print $key, "\t", average($HoA{$key}), "\n";
}

sub average {
    my $array_ref = shift;
    my $sum;
    foreach (@$array_ref) {
        $sum += $_;
    }
    my $av = $sum / @$array_ref;
    return $av;
}