一、if语句
例如：
二、while语句
例如：
例如：
if ($name gt 'fred') {
print "'$name' comes after 'fred' in sorted order.\n";
} 同样也有else：
if ($name gt 'fred') {
print "'$name' comes after 'fred' in sorted order.\n";
} else {
print "'$name' does not come after 'fred'.\n";
print "Maybe it's the same string,in fact.\n";
}
二、while语句
例如：
$count = 0;
while ($count < 10) {
$count += 2;
print "count is now $count.\n"; # 程序将依次打印出2,4,6,8,10
}