1. 半徑為12.5時枷餐，圓的周長應(yīng)該是多少？
#!/usr/bin/perl
$radius = 12.5;
print $radius * 2 * 3.141592654."\n";
2. 修改上題苫亦，提示用戶鍵入半徑毛肋，求出圓的周長。
#!/usr/bin/perl
print "Please input the radius of the circle: ";
$radius = <STDIN>;
print "The perimeter of the circle is: ";
print $radius * 2 * 3.141592654."\n";
3. 修改上題著觉，當(dāng)用戶輸入小于0的半徑時，輸出0而不是負數(shù)惊暴。
#!/usr/bin/perl
print "Please input the radius of the circle: ";
$radius = <STDIN>;
print "The perimeter of the circle is: ";
if ($radius lt 0) {
print "0"."\n";
}else {
print $radius * 2 * 3.141592654."\n";
}
4. 提示用戶輸入兩個數(shù)字饼丘，求兩者的乘積？
#!/usr/bin/perl
print "Please input the first number: ";
$num_1 = <STDIN>;
print "Please input the second number: ";
$num_2 = <STDIN>;
$result = $num_1 * $num_2;
print "The product of the two numbers is: $result\n";
5. 用戶鍵入一個字符串和一個數(shù)字辽话，以數(shù)字為重復(fù)次數(shù)肄鸽，連續(xù)輸出字符串。
#!/usr/bin/perl -W
print "Please input a string: ";
$string = <STDIN>;
print "Please input a positive number: ";
$num = <STDIN>;
$result = $string x $num;
print "The result is:\n$result";
