Perl Learning Notes (iv)--subroutines

To define a sub-program :

To define your own subroutine, you can use the keyword sub, the subroutine name (not including the number), and the block of code enclosed in curly braces, for example:

1 Sub marine{2      $n + =1;  # global variable $n 3      Print $n \n "; 4 }

Subroutines do not need to be declared beforehand

The definition of a subroutine is global and there is no private subroutine

If you define two sub-programs with the same name, the following subroutine overwrites the

Calling a sub-program

1 &marine;

return value

The result of the last operation in the subroutine is automatically treated as the return value of the subroutine.

Parameters

To pass a list of arguments to a subroutine, simply add a list expression that is enclosed by parentheses after the subroutine call, for example:

1 $n = &max (N);

Private variables in sub-programs

By default, all of the variables in Perl are global variables, and you can use the My operator to create private variables, which we call lexical variables

1  Submax{2      my($m,$n);#The new private variable in the statement block3($m,$n) =@_;#Assigning a parameter to a variable4      If($m>$n){$m}Else{$n}    5}

the improved &max Sub-Program

1 $maxinum=$max(3,5,Ten,4,6);2 Submax{3     my($max _so_far) =Shift @_;#the first value in the array, temporarily treating it as a maximum value4     foreach(@_){#traversing other elements in the array @_5      if($_>$max _so_far){#is the current element larger than $max_so_far?6          $max _so_far=$_;7      }8     }9     $max _so_far;Ten}

Use Strict Compiling Instructions

More rigorous code and compilation style

return operator

Immediately stop executing the subroutine and return a value

Perl Learning Notes (iv)--subroutines