use B 'svref_2object';
$rv = \"hello kitty";
$rv_obj = svref_2object( $rv );
$rv_address = B::address( $rv_obj );

$sv_any = unpack 'P4', $rv_address; # It fails here
$rv_address += 4;
$sv_refcnt = unpack 'P4', $rv_address; # or here if I just increment the address
$rv_address += 4;
$sv_flags = unpack 'P4', $rv_address; # or anywhere I try using unpack 'P'
printf "%08x\n%08x\n%08x\n", $sv_refcnt;