第二章：标量数据

1)
$pi=3.141592654;
$radius=12.5;
$circumference=2*$pi*$radius;
print "Circumference is $circumference.\n";

2)
$pi=3.141592654;
print "Please input a radius: ";
$radius=<STDIN>;
$circumference=2*$pi*$radius;
print "Circumference is $circumference.\n";

3)
$pi=3.141592654;
print "Please input a radius: ";
$radius=<STDIN>;
if ($radius < 0){
 $radius=0; 
}
$circumference=2*$pi*$radius;
print "Circumference is $circumference.\n";

4)
print "Please input a 1st number: ";
chomp($firNum=<STDIN>);
print "Please input a 2nd number: ";
chomp($secNum=<STDIN>);
#chomp($firNum);
#chomp($secNum);
$plus=$firNum*$secNum;
print "$firNum * $secNum is $plus.\n";

5)
print "Please input a string: ";
$str=<STDIN>;
print "Please input a number: ";
$num=<STDIN>;
#chomp($num);
$strSum=$str x $num;
print $strSum;