use strict;
use warnings;
use Devel::Peek;


use Inline C =><<'EOC';

void foo(SV * sv) {
  printf("\n%s\n\n", SvPV_nolen(sv));
/*
  SvPOK_off(sv);
  SvPV_set(sv, NULL);
*/
}

EOC

my $sv = 12345;

Dump $sv;
foo($sv);
Dump($sv);

__END__

Outputs:

SV = IV(0x4ecd70) at 0x4ecd80
  REFCNT = 1
  FLAGS = (IOK,pIOK)
  IV = 12345

12345

SV = PVIV(0x4f0088) at 0x4ecd80
  REFCNT = 1
  FLAGS = (IOK,POK,pIOK,pPOK)
  IV = 12345
  PV = 0x25a4448 "12345"\0
  CUR = 5
  LEN = 10

##</code><code>##

SV = PVIV(0x4f0088) at 0x4ecd80
  REFCNT = 1
  FLAGS = (IOK,pIOK)
  IV = 12345
  PV = 0