use Config      qw( %Config );
use Devel::Peek qw( Dump );

my $ptr_size = $Config{ ptrsize };
my $ptr_format =
   $ptr_size == 4 ? "L" :
   $ptr_size == 8 ? "Q" :
   die( "Unsupported pointer size $ptr_size\n" );

# https://perldoc.perl.org/perlapi#SvPV_force
sub SvPV_force { unpack $ptr_format, pack "P", $_[0] }

my $s = "abc";
Dump $s;
printf "%x\n", SvPV_force( $s );
Dump $s;