my $qr    = qr/^$alpha$alnum+$/;

[snip]

sub testsubqr {
  my $count = 0;

  foreach (@words) {
    $count++ if(/$qr/);
  }
  return $count;
}

sub testsubqro {
  my $count = 0;

  foreach (@words) {
    $count++ if(/$qr/o);
  }
  return $count;
}