MAIN: {
    my $cgi = CGI->new();
    my $session = CGI::Session->new(...);
    my $dbh = $dbh->connect(...);

    my $result = do_something($cgi, $session, $dbh);

    print $cgi->header().$result;
}

sub do_something {
    my ($cgi, $session, $dbh) = @_;

    $dbh->foo(...);
    $cgi->bar(...);

    my $foo = another_subroutine($cgi, $dbh, $somevar, $othervar);

    return final_result ($cgi, $session, $foo);
}

sub another_subroutine {
    my ($cgi, $dbh, $somevar, $othervar) = @_;

    return $dbh->baz($cgi, $somevar, $othervar);
}

sub final_result {
    my ($cgi, $session, $foo) = @_;

    my $result = # operations with $cgi, $session and $foo

    return $result;
}