my $arg;
if(defined $status) {
	$statement = 'SELECT COUNT(*) FROM name WHERE status=?;';
	$arg = $status;
} else {
	$statement = 'SELECT COUNT(*) FROM name WHERE age=?;';
	$arg=4;
}

$sth = $dbh->prepare($statement) or die "Cannot Prepare $DBI::errstr";
$sth->execute($arg) or die "Cannot execute $DBI::errstr";