use strict;
use warnings;
use feature qw( say );

use Inline C => <<'__EOI__';

IV get_interpreter_id() {
   return (IV)PERL_GET_THX;
}

__EOI__

say get_interpreter_id();

##</code><code>##

>perl a.pl
3092452

##</code><code>##

#include "EXTERN.h"
#include "perl.h"
#include "XSUB.h"

MODULE = Foo  PACKAGE = Foo

IV
get_interpreter_id()
   CODE:
      RETVAL = (IV)PERL_GET_THX;

   OUTPUT:
      RETVAL