#This is the SWIG generated module to my C library
use MyModule;
#shared scalar
$cb_done = 0;

#This cb would be invoked by the cloned interpreter in the
#C library.  This works fine.
sub cb_one
{
  ($event, $pdata) = @_;
  #This line is printed.
  print "event : ", $event, "\n";
  $cb_done = 1;
}

$status = MyModule::RegisterCB(\&main::cb_one);

do
{
   sleep (5);
} until ($cb_done == 1)

#This line is not printed as $cb_done never becomes 1 
#in the main of the perl script
print "CB was invoked : $cb_done\n";

##</code><code>##

use threads;
use threads::shared;

use MyModule;
#shared scalar
$cb_done : shared = 0;