Problem in CGI Session

[d0353101]

I am having login.cgi. user enter id and password. if ok it redirects to main.cgi with user_id as main_page.cgi?u ser_id=$user_id .

main.cgi is having left menu and right part is for doing some action.

in all the CGI files including main.cgi I am writing this code before start_html to manage the session:

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my $cgi = CGI->new;

my $login_user_id = $cgi->param('user_id');    

########### -- Creating The session--##################

my $session = CGI::Session->new( undef, $cgi, {Directory=>'/tmp'} );
my $cookie = $cgi->cookie(CGISESSID => $session->id );
print $cgi->header(-cookie=>$cookie);

print $cgi->start_html("ADD CATEGORY");

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But when I click any link (like add payment) on the left menu. a new session is getting created every time.

Please help... I dont want a new session.

I m stuck in it since last 2 days and getting dumbheaded. Please help :-(