new to PERL: explain a procedure

Posted on 2008-10-17
Last Modified: 2012-06-22
Hello : I AM totally new to PERL
I have to change some functions in a website written in PERL.
Can someone explain me step by step(line by line) what this function does ?
   $Session = CGI::Session->new($SESSION_DSN, $source || $class->genRef, $SESSION_ARGS)

(I do use PHP)


sub create_session {
    my ($class, $source) = @_;
    my $Session;
    do {
        $Session && warn "COOKIE exist: $source !";

        $Session = CGI::Session->new($SESSION_DSN, $source || $class->genRef, $SESSION_ARGS)
            or die CGI::Session->errstr;
    while (
        not($source) && not($Session->is_new)

    return $Session;
Question by:yarek
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1 Comment
LVL 39

Accepted Solution

Adam314 earned 500 total points
ID: 22741046
For more details on CGI::Session, see here:

#define a subroutine, named create_session
sub create_session {
    #Get the first passed parameter as $class, the second as $source
    my ($class, $source) = @_;
    #define a variable $Session, with no value
    my $Session;
    #Beginning of a loop
    do {
        #If $Session is defined, display a warning
        $Session && warn "COOKIE exist: $source !";
        #Set $Session to a new CGI::Session
        #For that new object, use $SESSION_DSN as the data source
        #if $source is defined, use that for the session id, otherwise use $class->genRef
        #use $SESSION_ARGS as options
        #If creating the object failed, die (exit with error value) displaying an error message
        $Session = CGI::Session->new($SESSION_DSN, $source || $class->genRef, $SESSION_ARGS)
            or die CGI::Session->errstr;
    #Continue trying that while $source is not defined, and $Session is not new
    while (
        not($source) && not($Session->is_new)
    #Return $Session to the calling procedure
    return $Session;

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