use feature qw( say );
use B qw( );

my ($f,$g) = (333,"xyz");
say B::class(B::svref_2object(\$f));
say B::class(B::svref_2object(\$g));

##</code><code>##

IV
PV

##</code><code>##

use feature qw( say );
use B qw( );

$_ = 333;
"".$_;
$_ = undef;
say B::class(B::svref_2object(\$_));

##</code><code>##

PVIV