Please Help, Perl Subroutines!

Hey,

I am learning Perl but I just cannot quite understand how the subroutines (Functions) work in Perl

Here are some examples of a script and if someone could explain it line by line and how it is doing what it is then I would really appreciate it

use strict;
sub HowdyEveryone {
   my($name1, $name2) = @_;
   return "Hello $name1 and $name2.\n" .
          "Where do you want to go with Perl today?\n";
}
print &HowdyEveryone("bart", "lisa");

Code (markup):

Source: http://www.faqs.org/docs/pperl/pickingUpPerl_8.html

Thanks in advance!

 

Ok, I will try to explain:

use strict;

PHP:

Tells PERL to check if every variable is defined before it is used. If you just start using a variable without declaring it with "my", the script will crash.

print &HowdyEveryone("bart", "lisa");

PHP:

This is first real line that is executed. It tells PERL to call the function HowdyEveryone with 2 parameters "bart" and "lisa" and print the result to the screen.

sub HowdyEveryone {
   my($name1, $name2) = @_;
   return "Hello $name1 and $name2.\n" .
          "Where do you want to go with Perl today?\n";
}

PHP:

This is the subroutine. "@_" is an array with the 2 variables "bart" and "lisa", ($name1, $name2) is also an array because of the brackets (). "bart" becomes $name1, "lisa" $name2. Other ways to do the same:

my $name1 = shift;
my $name2 = shift;

PHP:

The effect is the same. "shift" shifts the elements in the array @_
or:

my $name1 = $_[0];
my $name2 = $_[1];

PHP:

The next 2 lines return a text with the 2 variables. "return" always ends the function. The text is printed to the screen because of the "print" statement outside the function.

 

Ah ok, that makes much more sense to me now, I think am almost there, just one other question though.

What is the using "my" about in the subroutine?

I don't understand what it is and what it does there.

Thank you for your explanation, much appreciated!

 

The "my" keyword changes the scope of a variable. Using it inside the function makes the variable local to the subroutine.