can you explain a little bit for me

[maverickx]

Hi, i am totally new to perl.
I saw one example script but can't figure some syntax out, could you help out.

    $collected = Get_Friends($id,$name,"$profile_file",$limit,$collected); 
    $profile_file =~ s/>//;                
 

These codes are in one subroutine, and these is another subroutine called Get_Friends., are these variables in the square parameters like JAVA, C#. And what does =~s mean ?

thanks in advanced

[KevinADC]

The second line is a regular expression. "=~" is the binding operator. It is similar to "=" but return the values of a regular expression to the variable on the left instead of simply assigning a value like "=" does. s/// is the substitution regular expression. In the that line:

$profile_file =~ s/>//;

it is substituting the first instance of '>' in $profile_file with nothing,. so it is removing it.

The first line is calling the subroutine Get_Friends(). The data in the parenthesis to the right of the subroutine name are the arguments sent to the subroutine, the value returned is assigned to $collected on the left of the "=" symbol.

[maverickx]

thank you very much.

I just had a look at the tutorial of perl, but still have some confusions

what does @ represent?
my $id = shift; what does this mean?

and $1,$2 what are these variables meaning?

[KevinADC]

@ usually defines an array

"shift" is a function that removes and returns the first element of an array. If no array is used with the function it removes and returns the first element of the system array: @_, which is used to pass arguments to subroutines. Perl has two very special variables:

$_
@_

whenever a perl functon is used without a specific variable perl almost always assumes $_ or @_ depending on the context. Which is why something like this works:

for (@array) {
   print;
}

the print function is not using any argument so perl assumes $_. Same with the for() loop. Perl assigns each element of @array to $_ if you do not specify a variable like below:

foreach my $var (@array) {
   print $var;
}

Dont get into the habit of using $_ and @_ too much and relying on perl to do what is right. At first it seems tempting to write code like the first example above, but in reality it's not good practice.

$1 and $2 (up to $9 I believe) are special variables perl uses to store pattern matches of regular expressions in memory. They are read only variables, which means they can not be modifed inplace.

$foo = 'foo';
$foo =~ m/^(.)/;
print $1; (prints 'f');

Your questions above indicate you are jumping around considerably. Data types should be the first chapter or near first of any perl tutorial or book. Stuff like "shift" and $1 will come later after you are familiar with the basic stuff.

You should read a perl book, here is a free online book:

Beginning Perl