Perl Learning Record

1. Sub-Program

Define subroutines: The keyword sub, the subroutine name (not included with the number), and the block of code enclosed with curly braces, which is the main body of the program;

Sub marine{

$n +=1;

Print "Hello,sailor number$n!\n";

}

The definition of a subroutine is global.

2. Calling subroutines

The subroutine name (preceded by a number) can be used in any expression to invoke it;

&marine;

3. Return value

In Perl, all subroutines have a return value-the subroutine does not have a "return value" or "no return value", but not all Perl programs contain useful return values;

For example, we define the following subroutine, and the last one is the addition expression:

Sub sum_of_fred_and_barney{

Print "Hey, you called the Sum_of_fred_and Barney subroutine!\n";

$fred + $barney; #这就是返回值

}

$fred = 3;

$barney = 4;

$wilma =&sum_of_fred_and_barney;

4. Parameters

Perl subroutines can have parameters. To pass the argument list into the subroutine, simply add the list expression after the subroutine call with the parentheses around it.

$n =&max (10,15); #包含两个参数的子程序调用

Perl automatically aliases the parameter list as a special array variable @_, which means that the first parameter of the subroutine is stored in $_[0], and the second parameter is stored in $_[1]

Sub max{

if ($_[0]>$_[1]) {

$_[0];

}

else{

$_[1];

}

}

Perl Learning Record